Make root crate tests fail on a missing fixture or axis, never skip

[MattJackson]

Status row 114, the root crate's share (row 114b). No test in crates/busbar passes by returning early when its subject is absent.

What changed (tests only)

• One panic per missing fixture: crates/busbar/tests/common/plugins.rs::missing(name, command) -> ! panics with the <name> cdylib is not built: run first (this test never skips). The commands are BUILD_BUSBAR_EXAMPLES (cargo build -p busbar --examples), BUILD_LOADER_EXAMPLES (cargo build -p busbar-plugin-loader --examples) and BUILD_PINNED (cargo test -p busbar --no-run). The root unit tests already mount this file as crate::root::test_plugins, so they call the same helper. No second copy exists.
• Fixture probes return the artifact or panic, in every run. Every std::env::var_os("CI") special case is gone:
  • serve_planes::dropped_path / bound;
  • serve_money::governed* (they return Governed, not Option) and neutral_framers;
  • registry::dropped_doors;
  • export_plugin_dropped_in_serves::export_cdylib, export_scrape_is_first_party::metrics_sink_cdylib and transport_dropped_in_serves::transport_cdylib;
  • the tcp drop-in in linked_export_sinks_boot_as_their_own_kind and the otlp cdylib in traces_stream_both_doors;
  • plane_driver::dropped_path / plane_rider::dropped_path. Their ways() always include Dropped, so the dropped door is no longer skipped quietly.
  • Every let Some(x) = probe() else { eprintln!("skip: …"); return; }; is now let x = probe();.
• mcp_stdio_serve.rs: install_auth_plugin returns () and panics when the cdylib is absent. record_skip, BUSBAR_TEST_SKIP_LEDGER and the ledger text are deleted.
• store_adapter_verb_seam.rs: adapter_over_published_schema() and adapter_at() return StoreAdapter. The 8 dead guards are deleted.
• Linkage probes are now gates. Each attribute sits beside its #[test], and the test asserts its subject inside:
  • export_otlp_delivers_spans: #[cfg(all(feature = "transport-tcp", feature = "export-otlp"))] with assert!(LINKED_TRANSPORTS…tcp) and assert!(otlp_linked(&dir));
  • traces_stream_both_doors: #[cfg(feature = "transport-tcp")] with the tcp assertion;
  • linked_export_sinks_boot_as_their_own_kind: #[cfg(linked_axis_export_doors)] with assert!(!sinks.is_empty());
  • migration_corpus (both tests): #[cfg(feature = "auth-admin-tokens")];
  • cli_validate::validate_orders_a_webhook_sinks_refusals_among_the_limits_as_before: #[cfg(all(linked_axis_body_ingress, feature = "export-webhook"))] with assert!(!probed.contains("unknown exporter 'request-log-webhook'"), "{probed}");
  • plane_isomorphism (both tests): see the judgment call below, with assert!(!decls.is_empty()).
• Left unchanged as the task says: serve_money.rs NODE_HOOKS_ARM (the re-exec harness).

Judgment calls

• plane_isomorphism is gated on #[cfg(linked_axis_plane)], not linked_every_plane. The probe was installed_decls().is_empty(), and LINKED_PLANES holds exactly the enabled rows that carry the plane axis. linked_axis_plane is the build-script cfg that names that subject. linked_every_plane would also stop compiling both tests on every partial-plane build. The test bodies pass cfg!(linked_every_plane) into verify_scoped so that partial rosters still run. every_installed_plane_is_answered_by_a_root_leg's doc says it must run on every build, and "used to be cfg-gated … ran in exactly one build configuration" is the regression it records.
• More var_os("CI") sites than the table lists (plane_driver.rs, plane_rider.rs, serve_money::neutral_framers, the tcp and otlp drop-ins). Scanner rule (b) refuses every one of them, so they are converted the same way.
• Unit-test helper: the task asked for a sibling helper in src/root/tests/. The root tree already mounts tests/common/plugins.rs as crate::root::test_plugins, so it calls the same missing instead of keeping a copy.
• Scanner rule (d) also follows a plain let binding of a probe's answer, e.g. let decls = installed_decls(); if decls.is_empty() { return; }. Without that, the plane_isomorphism and linked_export_sinks guards would get past it.

Tests

• crates/busbar/tests/no_silent_skip.rs scans every .rs under src/root/tests/ and tests/ (itself excluded). Comments are stripped by common::classify. It fails and lists file:line on:
  • (a) a skip:/SKIP print;
  • (b) var_os("CI")/var("CI");
  • (c) record_skip(;
  • (d) a let-else or if guard that only prints and return;s, around a probe name or cfg!(feature.
• Two selftests show the scan can say no. Every removed shape is refused by its rule, and every replacement shape passes: the panicking probe, the #[cfg] with its assertion, a non-probe guard, and a guard that does more than skip.
• RED arm of the helper: root::serve::planes_tests::a_missing_fixture_cdylib_fails_the_test_and_names_its_build is #[should_panic(expected = "is not built: run")].

RED: what the scanner reports at the base (origin/predev 39374ec)

The lane rules forbid building or running tests locally, so this list was not produced by a run of the scanner. It was derived by applying the scanner's rules with git grep at the base commit and reading the guard sites. CI runs the real thing on this head. At the base the test fails with N silent skip(s): …, followed by:

src/root/tests/registry.rs:862: (b) a fixture that fails only under CI
src/root/tests/registry.rs:929: (d) a let-else whose else only skips
src/root/tests/registry.rs:930: (a) a print announcing a skip
src/root/tests/registry.rs:965: (d) a let-else whose else only skips
src/root/tests/registry.rs:966: (a) a print announcing a skip
src/root/tests/serve_framed.rs:67,92,110,148,201,220: (d) a let-else whose else only skips
src/root/tests/serve_framed.rs:68,93,111,149,202,221: (a) a print announcing a skip
src/root/tests/serve_money.rs:357,378,393,411,432,481,502,522,563,587,607,720,782: (d) a let-else whose else only skips
src/root/tests/serve_money.rs:358,379,394,412,433,482,503,523,564,588,608,730,783: (a) a print announcing a skip
src/root/tests/serve_money.rs:892: (b) a fixture that fails only under CI
src/root/tests/serve_planes.rs:60: (b) a fixture that fails only under CI
src/root/tests/serve_planes.rs:125,174: (d) a let-else whose else only skips
src/root/tests/serve_planes.rs:126,175: (a) a print announcing a skip
tests/export_otlp_delivers_spans.rs:138,145: (d) an `if` guard whose body only skips
tests/export_plugin_dropped_in_serves.rs:52: (b) a fixture that fails only under CI
tests/export_plugin_dropped_in_serves.rs:170,289: (d) a let-else whose else only skips
tests/export_plugin_dropped_in_serves.rs:171,290: (a) a print announcing a skip
tests/export_scrape_is_first_party.rs:47: (b) a fixture that fails only under CI
tests/export_scrape_is_first_party.rs:225: (d) a let-else whose else only skips
tests/export_scrape_is_first_party.rs:226: (a) a print announcing a skip
tests/linked_export_sinks_boot_as_their_own_kind.rs:179: (d) an `if` guard whose body only skips
tests/linked_export_sinks_boot_as_their_own_kind.rs:197: (b) a fixture that fails only under CI
tests/mcp_stdio_serve.rs:166: (c) a skip ledger
tests/mcp_stdio_serve.rs:172: (b) a fixture that fails only under CI
tests/mcp_stdio_serve.rs:220: (c) a skip ledger
tests/mcp_stdio_serve.rs:500,524,549,631,664,734: (d) an `if` guard whose body only skips
tests/migration_corpus.rs:363,526: (d) an `if` guard whose body only skips
tests/migration_corpus.rs:364,527: (a) a print announcing a skip
tests/plane_driver.rs:73: (b) a fixture that fails only under CI
tests/plane_isomorphism.rs:344,406: (d) an `if` guard whose body only skips
tests/plane_rider.rs:62: (b) a fixture that fails only under CI
tests/store_adapter_verb_seam.rs:128,147,160,201,229,243,309,341: (d) a let-else whose else only skips
tests/traces_stream_both_doors.rs:127: (d) an `if` guard whose body only skips
tests/traces_stream_both_doors.rs:132: (b) a fixture that fails only under CI
tests/transport_dropped_in_serves.rs:68: (b) a fixture that fails only under CI
tests/transport_dropped_in_serves.rs:278: (d) a let-else whose else only skips
tests/transport_dropped_in_serves.rs:279: (a) a print announcing a skip

Comma-separated line numbers stand for one row each. cli_validate.rs:1673 is converted by this PR but is not a scanner finding at the base: its probe, run_busbar, is not on the (d) name list.

PR #590 and PR #570 (auth_plugin_chain.rs) had not merged when this branched, so neither is touched.

[github-actions]

promote into predev: all green @b673ae7b0

Already red on predev, not this PR's: 10

gate	row	detail
construction	one-pick-site	3 production call site(s) of 'pick_among(' (ceiling 2): crates/busbar-kernel-egress/src/walk.rs:298; crates/busbar-llm/src/engine/exhaustion/fallback.rs:120; crates/busbar-llm/src/engine/pipeline.rs:8
kind-isolation	kind-isolation:deps	3 finding(s), 93 shipped edge instance(s) over 30 class(es), 93 declaration(s); 56 '[[dep]]' row(s), 0 question(s): unlisted-dep-edge legacy -> plane busbar-llm -> busbar-plane-llm is a shipped edge w
kind-isolation	kind-isolation:law0	5 hit(s) off the [[law0]] ceilings, 3 finding(s) over 14 neutral crate(s): law0-rise busbar × instance:secret 37 hit(s) against a ceiling of 35: this landing grew a neutral crate's instance vocabulary
kind-isolation-ship	kind-isolation:deps	10 finding(s) over 93 shipped edge(s): ship-edge kernel -> hooks busbar-kernel -> busbar-hook-ranking is 'not-allowed': the architecture grants no kernel -> hooks edge, and the ship criterion is the a
kind-isolation-ship	kind-isolation:test-deps	8 finding(s) over 32 test edge(s): ship-edge cleanliness -> export busbar-core-admin -> busbar-export-prometheus is 'not-allowed': the architecture grants no cleanliness -> export edge, and the ship c
kind-isolation-ship	kind-isolation:law0	5 hit(s) off the [[law0]] ceilings, 3 finding(s) over 14 neutral crate(s): law0-rise busbar × instance:secret 37 hit(s) against a ceiling of 35: this landing grew a neutral crate's instance vocabulary
kind-isolation-ship	kind-isolation:faces	2 finding(s) over 40 crate(s): foreign-entry crates/busbar busbar is kind 'root' and implements 'Transport' 1 time(s) in shipped source — the entry face of kind 'transport'. A trait implementation is
kind-isolation-ship	kind-isolation:legacy-drain	3 finding(s): transitional-live qa/kind-isolation.toml 'busbar-a2a -> busbar-core-admin' (legacy drain: the retiring A2A engine's tests drive the admin surface that drained into the cleanliness tier)
ship-ready	ship-ready:ship-twin	'kind-isolation-ship' is not green: kind-isolation:deps (a dependency the architecture does not grant is still in the graph); kind-isolation:test-deps (a dependency the architecture does not grant is
structure-lint	structure-lint:plane-dup:unledgered	22 finding(s): PLANE-DUPLICATE (module): 'config.rs' — a2a:crates/busbar-a2a/src/a2a/config.rs decisions:crates/busbar-plane-decisions/src/config.rs voice:crates/busbar-voice/src/config.rs (the ledger

tests passed: 5296, failed: 0. Run: https://github.com/GetBusbar/busbar/actions/runs/38276974807 . Artifact verdict-b673ae7b0b4cb7921b3e8c0e751fbcf58938c0e1 (failures.json, junit.xml, raw.log; 90 days).

[MattJackson]

Claim released by busbar-release: the fixing label had no live agent behind it: no push and no new claim for 18h03m (the longest agent's hard timeout is 2h00m), so it is off and the PR is back in the pipeline.

[MattJackson]

Re-run by busbar-release: the engine pin ENGINE_REF 937eae641 now contains busbar-release 5a1380d, which the owner question this PR was held on names; the failed jobs of 0e1090f are re-run and the hold is lifted.