no-silent-skip sweep (status row 114): scrape-sink test gated on its feature

[MattJackson]

Status row 114: no test in crates/ passes by an early-return skip when its subject is absent in the default build.

Sweep: every #[test]/#[tokio::test] body scanned for early return, plus eprintln!("skip..."), var("CI") and env opt-outs. Most of the tree was already clean (the per-crate no_silent_skip scans exist in busbar, busbar-kernel, busbar-core-admin, plugin-loader).

Changed (the site is in files no open PR touches):

• crates/busbar/src/root/tests/linked.rs:561 (the_linked_scrape_sink_renders_the_recorder_snapshot_byte_identically): if module.is_empty() || registry.resolve(module).is_none() { return; }. The sink is linked by default feature export-prometheus (case b): the test is now #[cfg(feature = "export-prometheus")] and the guard is two asserts, so an absent sink fails loudly.

Left: crates/busbar-llm forward_pool_integration_tests.rs:60 (capture_latency_metrics env opt-in) because row 155 deletes the crate.

Found but NOT changed, because an open PR touches the file:

• crates/busbar-core-connector/tests/universal_needs.rs:262-267 (door absent and not CI returns; row 130 E6: the plugins.fetch download leaves busbar-kernel and rides the one connector (stacked on #804) #805)
• crates/plugin-loader/src/conformance/auth/outbound.rs:1634, 1659, 1689, 1696 (print and return when the door states no outbound family / mints nothing; row 68: the breaker reads a plane fault at the far end (stacked on #561) #778, breaker: no protocol in kernel; the transport states its fault table, PIECE_END=128 rides the same framer lineage (row 66) #561)

Reviewed and left: crates/plugin-loader/src/conformance/mod.rs:1879 (needs_declared, no declares.json; plugin-ci owns presence, helper not a test); re-exec child-process guards (durability_amend.rs:78, serve_money.rs:663/688, loader_seam_tests.rs:144, dispatch_tests.rs:1560, stage_tests.rs:356) which are the parent/child halves of one test, not skips; retry/accept-loop and walker filters.

RED-able: removing the sink from the linked rows now fails the scrape test instead of passing.
No cargo run locally (rules); ModernCI is the proof.