chore(ci): replace secret-scanner.yml with reusable wrapper (#23)

## Summary
Replaces this repo's `secret-scanner.yml` (~75-116 lines) with a thin
~14-line wrapper calling
`hyperpolymath/standards/.github/workflows/secret-scanner-reusable.yml@3e4bd4c93911750727e2e4c66dff859e00079da0`
(merged via standards#190).

## Security debt closed
The `shell-secrets` job (added to the canonical 2026-05-21 in direct
response to the live Cloudflare API token leak via
`avow-protocol/deploy-repos.sh` — a leak both `trufflehog
--only-verified` and default `gitleaks` missed) was carried by 0 of 16
sampled estate copies. This PR brings that guardrail to this repo.

## Why now
Estate audit: 281 `secret-scanner.yml` deployments / 54 unique SHAs /
19% true drift. Drift is pin churn + whitespace; feature variance is
near-zero. Converging behind the reusable means the next post-incident
guardrail update propagates via one SHA bump.

`secrets: inherit` flows `GITHUB_TOKEN` through implicitly so the
`gitleaks-action` step doesn't fall back to anonymous (rate-limited)
mode.

Part of estate-wide convergence campaign 2026-05-26 (standards#199 /
#190).

Author: hyperpolymath

.github/workflows/secret-scanner.yml

@@ -6,10 +6,6 @@ on:
   push:
     branches: [main]
 
-# Estate guardrail: cancel superseded runs so re-pushes / rebased PR
-# updates do not pile up queued runs against the shared account-wide
-# Actions concurrency pool. Applied only to read-only check workflows
-# (no publish/mutation), so cancelling a superseded run is always safe.
 concurrency:
   group: ${{ github.workflow }}-${{ github.ref }}
   cancel-in-progress: true
@@ -18,26 +14,6 @@ permissions:
   contents: read
 
 jobs:
-  trufflehog:
-    runs-on: ubuntu-latest
-    steps:
-      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
-        with:
-          fetch-depth: 0
-
-      - name: TruffleHog Secret Scan
-        uses: trufflesecurity/trufflehog@37b77001d0174ebec2fcca2bd83ff83a6d45a3ab # v3
-        with:
-          extra_args: --only-verified
-
-  gitleaks:
-    runs-on: ubuntu-latest
-    steps:
-      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
-        with:
-          fetch-depth: 0
-
-      - name: Gitleaks Secret Scan
-        uses: gitleaks/gitleaks-action@ff98106e4c7b2bc287b24eaf42907196329070c7 # v2
-        env:
-          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+  scan:
+    uses: hyperpolymath/standards/.github/workflows/secret-scanner-reusable.yml@3e4bd4c93911750727e2e4c66dff859e00079da0
+    secrets: inherit