[thekevinbot]

Fixes #1018.

Stacked on #1023 (claude/1017-ofpf-threshold), which adds the max_lines = 100
config this PR's local runs read. Review that one first; GitHub retargets this to
main when it merges.

What

just preflight derives its (root, language, gate) matrix from the workflows, so
it should run locally exactly what CI runs. Three separate things broke that for
one-function-per-file — the gate that has been red on main since the @v0 tag
rolled and that nothing local was exercising.

1. The gate table did not know it. matrix.py maps gate names to CLI argv;
one-function-per-file was absent from both ROOT_GATES (the implicit set a lane
naming no gates: is held to) and GATES (the name-to-argv table). A lane that
named it raised KeyError rather than building an invocation.

2. Three lanes did not name it. gates: is an allowlist, so
internals-checks, internals-distcheck and plugins-embeddings were skipping
the gate in CI too. Their arrays now name it.

3. The local CLI was not the CLI CI runs. Two independent resolution drifts,
both silent:

• uvx testing-conventions / uv run --with testing-conventions fetch the
  PyPI wheel, which trails the npm release (0.0.104 against 0.0.111 as of this
  PR). It has no one-function-per-file subcommand at all, and it rejects
  one_function_per_file as an unknown key — which fails the whole config, so
  unit coverage and unit mutation went red on three python lanes against a
  config CI accepts.
• A bare npx testing-conventions is worse. npm resolves an unversioned name
  engine-aware, engines.node rose to >=24 at 0.0.87, and a launcher shim on
  an older node therefore resolves the last release below that floor — dozens of
  releases of rule changes behind, exiting 0 with no version banner to say so. CI
  never hits this because every job provisions node 24.

Both close with npx -y testing-conventions@latest. The python arm keeps
uv run --with testing-conventions around it, but for a different reason than
before: --with no longer resolves the CLI, it only puts the wheel's
testing_conventions package on the interpreter the gate hands to python3 -m,
which is the sole form the mutation adapter ships in. uv run also keeps the
package's own venv as the suite's interpreter (#706).

Verification

Before this PR, just preflight --gate one-function-per-file reported
0 failing pair(s), 0 skipped — because it derived nothing. It now derives and
runs 5 pairs (python-sdk, typescript-sdk, internals-checks, internals-distcheck,
plugins-embeddings), all green.

Full just preflight: 8 failing pairs before the launcher fix, 0 after
(excluding the pre-existing python-sdk integration-lint red tracked in #1024,
which is on main and not this PR's to fix).

Red proofs, both observed failing in CI for exactly the asserted behavior:

Commit	Run / job	Result
it_derives_..._for_a_lane_naming_no_gates	33656262464 / 100335465678	1 failed, 32 passed
it_derives_..._for_every_lane_naming_it	33657987400 / 100341235381	1 failed, 33 passed
launcher argv tests	19c23b4 / 100342777147	2 failed, 395 passed

uv run --project internals/checks pytest internals/checks/src internals/checks/tests -q → 464 passed.

E2E Verification

• Ran e2e suites locally for every affected SDK
• Python SDK e2e: N/A — no packages/ source changed
• TypeScript SDK e2e: N/A — no packages/ source changed
• Rust core e2e (if applicable): N/A — no packages/ source changed
• packages/python/e2e-attestation.json refreshed if packages/python changed — N/A
• packages/ts/e2e-attestation.json refreshed if packages/ts changed — N/A
• Command(s) run: just test-e2e-internals-checks (24 passed), just e2e-attest-internals-checks
• Result summary: the only package this PR changes is internals/checks, whose
  own e2e-verify gate is satisfied by the receipt committed here.

Changelog / Migrations

• Changelog fragment — N/A, skip-changelog on each commit. The changelog gate scopes to packages/ and plugins/; this PR touches internals/checks and three workflow files, and the gates: edits are CI config with no packaged behavior.
• Migration fragment — not required; no public API and no runtime behavior change.

Parity

No SDK public API touched, so PARITY.md is unchanged.