ci: pin GitHub Actions version comments to full semver

Renovate's helpers:pinGitHubActionDigestsToSemver preset reads version
comments to track updates. Major-only comments (e.g. # v6) produce
unhelpful changelog diffs like "v6 → v6". Full semver comments
(e.g. # v6.0.2) let Renovate show meaningful version changes.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.github/workflows/bump-version.yml

@@ -15,13 +15,13 @@ jobs:
       packages: write
     steps:
       - name: Check out
-        uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6
+        uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
         with:
           fetch-depth: 0
           token: "${{ secrets.PERSONAL_ACCESS_TOKEN }}"
 
       - name: Set up Python
-        uses: actions/setup-python@a26af69be951a213d495a4c3e4e4022e16d87065 # v5
+        uses: actions/setup-python@a26af69be951a213d495a4c3e4e4022e16d87065 # v5.6.0
         with:
           python-version: '3.11'