ci: enforce the checks the contributor rules already required

Four gates that were documented but unenforced, plus the flaky test that
made a full-suite run untrustworthy.

Rust lint/format: CLAUDE.md has required `cargo fmt` and `cargo clippy`
before every commit for as long as the rule existed, yet neither ran
anywhere in CI — the requirement rested on memory alone. Both now run in
build-and-test.yml and build-release.yml. rustfmt and clippy are already
baked into the builder image, so nothing is installed at job time.
`cargo fmt --all -- --check` is strict immediately (the tree is clean).
Clippy is advisory for now: ~51 pre-existing warnings mean `-D warnings`
would fail on unrelated work, so the step carries a TODO to flip the flag
once the backlog clears. A compile error still fails it, so it is not a
no-op.

Traceability threshold: MIN_THRESHOLD sat at 50 while real coverage was
86%, so nearly half the matrix could rot before the gate objected.
Ratcheted to 82 with the policy written down — it only ever goes up, and
is never lowered to make a red build pass. The same figure lives in
MIN_COVERAGE_PERCENT so `traces:coverage` gates locally on the same bar,
and a test fails if the two drift.

Dangling IDs: a TRACES comment could name any well-formed ID and the
extractor accepted it silently, so typos and renames that missed a call
site passed unnoticed. `bun run traces:validate` cross-checks every
traced ID against the table rows in requirements.md and fails with the
referencing files listed. It spans UT/IT as well, which the coverage
orphan list ignores by design. This currently reports DR-189 and UT-188,
which are being defined separately.

Flaky offlineCatalog test: the first dynamic import of the service paid
~1s to transform its dependency graph, charged to a test body against
vitest's 5s default. Alone it passed; under suite-wide contention it
timed out. The import is now warmed at collection time, so no test is
timing the compiler — the timeout is deliberately unchanged. The store
shim also drops subscribers from module instances discarded by
resetModules, which previously leaked across tests.

scripts/README.md

@@ -69,7 +69,8 @@ Extract requirement IDs (TRACES) from source code and generate a traceability ma
 bun run traces                    # Generate markdown report
 bun run traces:json              # Generate JSON report
 bun run traces:markdown           # Save to docs/traceability.md
-bun run traces:coverage           # Coverage gate — exits non-zero below 50%
+bun run traces:coverage           # Coverage gate — exits non-zero below the ratchet
+bun run traces:validate           # Dangling-ID gate — every traced ID must be defined
 ```
 
 The script scans all TypeScript, Svelte, and Rust files (plus `scripts/`)
@@ -84,6 +85,12 @@ derived from `docs/requirements.md` at run time; they are never hardcoded. An ID
 that appears in a `TRACES:` comment but is not defined in `requirements.md` is
 reported as *orphaned* and does not count toward coverage (see DR-093).
 
+**`bun run traces:validate` is the dangling-ID gate.** It fails if any traced ID
+— including `UT`/`IT`, which coverage deliberately ignores — is not defined as a
+table row in `requirements.md`, printing each offender with the files that
+reference it. Without it the extractor accepted any well-formed ID silently, so
+typos and renames that missed a call site went unreported for months.
+
 > **Removed:** `check-req-coverage.sh`, `check-test-coverage.sh`, and
 > `find-req-implementations.sh` were deleted in July 2026. They read an
 > undocumented `@req:` tag convention parallel to `TRACES:`, grepped `src-tauri/`
@@ -104,7 +111,8 @@ See [docs/traceability.md](../docs/traceability.md) for the latest generated map
 
 The traceability system is integrated with Gitea Actions CI/CD:
 - Automatically validates TRACES on every push and pull request
-- Enforces minimum 50% coverage threshold
+- Enforces a minimum coverage threshold (a ratchet: raise it, never lower it)
+- Fails on dangling IDs — traced but undefined in `requirements.md`
 - Warns if new code lacks TRACES comments
 - Generates traceability reports automatically