chore(scripts): remove three broken, orphaned traceability scripts

All three shared one root cause: an unscoped `grep -r src-tauri/`, which
walks ~40GB of target/ build artifacts.

- check-req-coverage.sh: also read README.md, which has held zero
  requirement rows since they moved to docs/requirements.md. Reported
  "Total Requirements: 1", zeros in every category, then printed
  "All requirements have implementations!" — the opposite of a warning,
  from an empty result set.
- check-test-coverage.sh: hung indefinitely, no output at all.
- find-req-implementations.sh: same hang.

None was referenced by CI, package.json, or the docs.

They were salvageable — the greps just needed scoping — but they read an
undocumented `@req:` / `@req-test:` tag convention parallel to `TRACES:`
(146 and 76 occurrences, described in no doc; CLAUDE.md documents only
TRACES). Repairing them would re-establish the second source of truth
that let "1 requirement" and "211 requirements" coexist unnoticed.
extract-traces.ts is now the single owner of coverage reporting.

The existing @req:/@req-test: comments are left in place: harmless as
prose, several encode useful test intent, and stripping 222 comments is a
large diff with no functional gain. They are simply no longer read.

scripts/README.md

@@ -69,13 +69,29 @@ 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%
 ```
 
-The script scans all TypeScript, Svelte, and Rust files looking for `TRACES:` comments and generates a comprehensive mapping of:
+The script scans all TypeScript, Svelte, and Rust files (plus `scripts/`)
+looking for `TRACES:` comments and generates a comprehensive mapping of:
 - Which code files implement which requirements
 - Line numbers and code context
 - Coverage summary by requirement type (UR, IR, DR, JA)
 
+**`bun run traces:coverage` is the supported way to check requirement coverage
+locally** — it runs the same computation CI does. Coverage denominators are
+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).
+
+> **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/`
+> unscoped (hanging on ~40 GB of `target/` artifacts), and in one case reported
+> "all requirements implemented" from an empty result set. `extract-traces.ts` is
+> the single source of truth for requirement coverage. See
+> [docs/specs/req-coverage-script-removal.md](../docs/specs/req-coverage-script-removal.md).
+
 Example TRACES comment in code:
 ```typescript
 // TRACES: UR-005, UR-026 | DR-029