fix(ci): the content scan could not match R-C2-01/02 — a digit in the workstream segment

Checked as part of closing the C2 coverage gaps, and it was live on main. The content
scan's pattern was `R-[A-Z]+-[0-9]+`, which CANNOT match an ID whose workstream segment
carries a digit: `[A-Z]+` consumes the `C` of `R-C2-01` and then demands a `-` where the
`2` is. `R-C2-01` and `R-C2-02` are the only two such IDs in
conformance/requirements/registry.yaml, and the scan was blind to BOTH.

REPRODUCED before the fix, on a throwaway repo whose only change is a manifest declaring
both IDs on real (non-comment) lines, in a path the map keys to nothing:

    $ REPO_ROOT=$T BASE_REF=main ci/touched-requirements.sh
    R-NET-06                     # the all-letter control ID was the ONLY output

It failed by UNDER-attributing, which is the fail-OPEN direction: a change that retyped a
`conformance.home.k3s/R-C2-01` tag, or a manifest self-declaring R-C2-02, contributed
those IDs to NOBODY, so the C2 tests were filtered out of the merge gate. Same defect
class as the map's `*) : ;;` arm — a miss that reads as "nothing touched".

Every other consumer in the repo already allowed the digit, which is why this was the lone
dissenter: test_requirements_for_path() twenty lines above in this same script,
conformance/lib/coverage.py, conformance/lib/status.py and conformance/lib/
run_l1_offline.py all use `R-[A-Z0-9]+-[0-9]+`. Aligned to that form, with the reason
recorded at the line.

SCOPE OF THE HOLE. path_requirements() has no arm for platform/homepage/* or
platform/headlamp/* either, so before this the ONLY route to R-C2-01/02 was detection rule
3 (editing the C2 conformance test itself). No path-map arm is added here: c2-root-surface
declares `scope: whole-repo`, so ci/l0.sh Stage 3b's --include-scope union selects it on
EVERY gate invocation regardless of the touched set — which is the right mechanism for an
invariant whose input surface is the whole tree, and strictly stronger than a two-component
path arm would be.

REGRESSION-TESTED, in ci/tests/touched-requirements.test.sh (the suite `make -C ci test`
runs): a fixture declaring R-C2-01 / R-C2-02 / R-OBS-04 from `notes/` — a path outside
path_requirements(), so the IDs can only come from the content scan — asserts both digit
IDs ARE attributed, that the all-letter form still is (control), and that a purely numeric
workstream is not invented (the pattern must not widen the gate on noise).

PROVEN TO DETECT BREAKAGE: with the pattern reverted to `R-[A-Z]+-[0-9]+` the suite reports
`FAIL (2 failed, 14 passed)` naming both C2 IDs as missing; restored, all three ci/ suites
pass (16 assertions in this one).

ALSO: conformance/tests/l0-static/whole-repo-invariants-wired/check.sh cites this pattern
in the comment explaining why its BOGUS_REQ fixture is lowercase. Citation updated so the
reasoning still reads true; the fixture is unaffected (grep -E is case-sensitive, and the
check still passes 26/26).

NOTE: another branch may be editing this same script concurrently. This is a one-line
change to one statement plus its comment — expect a trivial conflict and keep the
`[A-Z0-9]` form.

Co-Authored-By: Claude Opus 5 <[email protected]>

conformance/tests/l0-static/whole-repo-invariants-wired/check.sh

@@ -85,7 +85,7 @@ done
 # second would fail.
 # Deliberately LOWERCASE: conf_normalize_reqs() upper-cases it, so the selection behaves
 # identically — but the literal here does not match ci/touched-requirements.sh's content-scan
-# pattern `R-[A-Z]+-[0-9]+`, so editing this file does not attribute a nonexistent requirement
+# pattern `R-[A-Z0-9]+-[0-9]+`, so editing this file does not attribute a nonexistent requirement
 # to the change. (Same reason the synthetic fixture below carries no requirement label at all.)
 BOGUS_REQ="r-nosuchreq-99"
 sel_without="$(bash "$RUN_SH" --layer l0 --requirements "$BOGUS_REQ" --print-selection 2>/dev/null || true)"