feat(ci): supply-chain hygiene — secret gate on every PR diff, dependency review, OSV, dependabot, evidence-bar PR template

The repo owned a redaction engine and had zero CI-side secret scanning.
quality-gate.yml now pipes every PR diff's ADDED lines through our own
bin/gstack-redact (gate-secret-scan.mjs, taken from the fork — it dogfoods
the engine): HIGH findings fail the check, MEDIUM prints an advisory count
only (no human in CI to confirm), planted-bug fixtures excluded by pathspec.
Live-verified both directions: PEM key fails, clean diff and MEDIUM shapes
pass; ShellCheck (errors) covers the setup/build shell boundary and passes
today; bun audit gates critical advisories. Trigger is pull_request, never
pull_request_target.

dependency-review.yml adopts the hardened never-merged prior-art branch
(fail-on-severity high, workflow paths watched, tight perms) — verify the
dependency graph parses bun.lock with a canary bump before trusting the
gate. dependabot: weekly, grouped per ecosystem, capped PR counts; and
evals.yml image build/push now skips dependabot actors, whose read-only
GITHUB_TOKEN made every lockfile bump a permanently red check. OSV scans
weekly with a reasoned ignore file. All new workflow actions SHA-pinned.
Scorecard deliberately not taken (no consumer for the score).

The PR template front-loads the evidence bar (live proof, liveness
screenshot, no-ETHOS/voice-changes checklist); the unenforced DCO line is
dropped. bin/gstack-verify-gate ships OPT-IN (never registered by ./setup —
a Stop hook running the project's verify command after every turn is the
user's call), with the fork's tests adapted to pin exactly that.

Ported from time-attack/gstack (GStack 2) + our own prior-art branch.

Co-authored-by: Sina Matian <sina@time-attack.dev>
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

.github/workflows/osv-scanner.yml

@@ -0,0 +1,26 @@
+name: OSV Scanner
+
+on:
+  schedule:
+    - cron: '23 7 * * 1'
+  workflow_dispatch:
+
+permissions:
+  contents: read
+
+concurrency:
+  group: osv-scanner
+  cancel-in-progress: true
+
+jobs:
+  scan:
+    permissions:
+      actions: read
+      contents: read
+      security-events: write
+    uses: google/osv-scanner-action/.github/workflows/osv-scanner-reusable.yml@3adb4b14a2b0623876d18d863a498b785fb3752d # v2.3.8
+    with:
+      scan-args: |-
+        --include-git-root
+        --recursive
+        ./