fix(ci): grant secret-scanner reusable its requested job permissions

The reusable's gitleaks job requests pull-requests: write + actions:
read; a called workflow cannot exceed the caller's grant, so wrappers
granting only contents: read die at startup_failure on every run.
Estate sweep; root cause fixed in standards#472.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: hyperpolymath

.github/workflows/secret-scanner.yml

@@ -11,6 +11,14 @@ permissions:
   contents: read
 jobs:
   scan:
+    # The reusable's gitleaks job requests pull-requests: write (PR
+    # summary comments) and actions: read. A called workflow cannot
+    # exceed the caller's grant - without these, every run dies at
+    # startup_failure. See standards#472.
+    permissions:
+      contents: read
+      pull-requests: write
+      actions: read
     uses: hyperpolymath/standards/.github/workflows/secret-scanner-reusable.yml@3e4bd4c93911750727e2e4c66dff859e00079da0
     timeout-minutes: 10
     secrets: inherit
@@ -23,4 +31,4 @@ jobs:
       - name: TruffleHog Secret Scan
         uses: trufflesecurity/trufflehog@main
         with:
-          extra_args: --only-verified --fail
+          extra_args: --only-verified --fail