demo: trigger audit-freeze gate (throwaway, not for merge)

[Jerryvic911]

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[Jerryvic911]

Demonstration that the gate fires: #1

That's a throwaway PR (base: issue-158-audit-freeze, my open PR for
this issue — wraith-protocol#183) that temporarily activated the freeze window and
touched stellar/stealth-announcer/README.md, an in-scope path.

• Without the audit-approved label: Audit Freeze Gate failed.
• After adding the label: the same check passed on the same commit.

Not merged — it was only ever meant to trigger the gate for real. The
freeze activation was reverted on my feature branch afterward.

On the design point about a PR being able to edit its own freeze
window: I used both approaches you mentioned, not just one. Primary —
the workflow checks out the PR's base ref (not the default PR-merge
ref), and check.ts separately fetches ENGAGEMENT.md's content from
that same base SHA via the GitHub API, so a PR's edits to that file are
simply invisible to the check. Secondary (defense in depth) —
ENGAGEMENT.md is always treated as a frozen path in its own right
whenever a freeze is active, regardless of what freeze_paths lists, so
even if the first mechanism ever regressed, editing the file would still
require the label. Full writeup in scripts/audit-freeze/README.md on
wraith-protocol#183.