ci: reuse central Veritas advisory workflow

[briananderson1222]

Replaces the copied advisory readiness implementation with the organization reusable workflow.

Preserves pull_request, workflow_dispatch, and contents: read; the central workflow owns the 1.5.5 pin and 30-minute job timeout.

Pilot proof: kontourai/flow-agents#1123 completed advisory readiness and evidence upload successfully.

[github-actions]

Trust Verify needs attention

Trust Verify completed with result: failure.

Open the workflow run

Failure details

[bundle-required-no-declared-marker] delivery/DECLARED marker present but out of scope for this change — STALE-SCOPE SUSPECTED: 6 of 7 well-formed entries PARTIALLY matched (some conditions matched, at least one did not). An exemption covering this change plausibly exists and a condition has drifted — e.g. a rotated bot actor (#1011) — rather than this change having no exemption at all. Per-entry breakdown below.

This is advisory and non-blocking; it does not change the Trust Verify verdict or merge requirements.