infra: wire GitHub Actions CI to enable AIV packet immutable run-log permalinks (W1, c2-f82 aiv-audit)

[ImmortalDemonGod]

What

AIV spec §3.3 (Class A evidence) expects an immutable CI-run permalink bound to the head SHA in each packet. No CI infrastructure currently exists for the flashcore repository: gh was unavailable in the c2-f82 pipeline environment, so all three c2-f82 packets (PACKET_c2_f82_impl.md, PACKET_c2_f82_tests.md, PACKET_c2_f82_crv.md) used the sha256 hash-manifest substitute (.github/aiv-packets/evidence/c2-f82/MANIFEST.md) instead of a CI permalink. The substitute satisfies the structural bar but leaves the W1 gap open for future PRs.

Why deferred

Surfaced as W1 WARN in .aiv/verdicts/c2-f82/aiv-audit.md:

"No CI infrastructure exists in this environment (gh unavailable; no Actions run to reference) — so A-001's CI-permalink form is genuinely unobtainable, not merely costly."

The aiv-audit recommended: "file a documented exception / known-limitation per spec §10 for the absent CI-run permalink, noting CI infrastructure is not yet wired and the hash-manifest substitute is in place."

CI setup was out of scope for the F82 correctness fix.

Acceptance criteria

• GitHub Actions CI workflow is configured for the flashcore repository and runs pytest tests/ -q --tb=short on every PR branch
• gh CLI is available in the pipeline execution environment so packet authors can retrieve an immutable run URL
• Future AIV packets can cite a stable GitHub Actions run URL in Class A (e.g., https://github.com/ImmortalDemonGod/flashcore/actions/runs/<run-id>)
• The three c2-f82 packets are amended to either (a) cite the sha256 hash-manifest as a documented §10 exception with explicit rationale, or (b) re-run with CI available and replace the sha256 substitute with a permalink