fix(ci): align caller permissions with pinned reusables (secret-scanner, scorecards) (#299)

## Problem

Two workflows are `startup_failure` on main (runs 28549269067,
28549269182 at head 2909ca6), both from the same root cause class:
**caller-vs-reusable permissions drift**. When a caller grants the
reusable less than the reusable's own `permissions:` declarations
request, GitHub refuses to start the run.

## Fixes

**Secret Scanner** (`.github/workflows/secret-scanner.yml`)
The pinned reusable (`standards/secret-scanner-reusable.yml@d135b05`)
declares on its `gitleaks` job:

- `pull-requests: write` — gitleaks-action posts a PR summary comment
- `actions: read` — workflow-run metadata / PR-files endpoints

(the reusable's own header comment says callers must grant these). The
caller granted only `contents: read` workflow-wide. Fix: grant exactly
`contents: read` + `pull-requests: write` + `actions: read` on the
`scan` job.

**Scorecards** (`.github/workflows/scorecard.yml`)
The caller's job-level `permissions:` block (`security-events: write`,
`id-token: write`) **replaces** the workflow-level `read-all` entirely,
dropping `contents` to `none`. The pinned reusable
(`standards/scorecard-reusable.yml@d7c2271`) declares workflow-level
`contents: read` (checkout needs it). Fix: restate `contents: read` in
the job-level block.

Minimum-necessary grants only — no `write-all`, nothing beyond what each
pinned reusable declares.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

Author: hyperpolymath

.github/workflows/scorecard.yml

@@ -12,8 +12,12 @@ permissions: read-all
 
 jobs:
   analysis:
+    # Job-level permissions REPLACE the workflow-level read-all block, so
+    # contents: read must be restated here — the reusable declares it
+    # (checkout needs it) and startup-fails if the caller doesn't grant it.
     permissions:
       security-events: write
       id-token: write
+      contents: read
     uses: hyperpolymath/standards/.github/workflows/scorecard-reusable.yml@d7c22711e830e1f383846472f6e9b99debdb201e # main 2026-05-28 (SPDX bump #249)
     secrets: inherit

.github/workflows/secret-scanner.yml

@@ -15,5 +15,12 @@ permissions:
 
 jobs:
   scan:
+    # The reusable's gitleaks job requests pull-requests: write (PR summary
+    # comment) and actions: read (workflow-run metadata) at job level; the
+    # caller must grant at least that or the run startup-fails.
+    permissions:
+      contents: read
+      pull-requests: write
+      actions: read
     uses: hyperpolymath/standards/.github/workflows/secret-scanner-reusable.yml@d135b05bfc647d0c0fbfedc7e80f37ea50f49236 # main 2026-05-28 (SPDX bump #249 + pragma/.shell-secrets-ignore fix #236)
     secrets: inherit