chore: fix claude.yml permissions and update actions versions

Grant pull-requests and issues write access so Claude can post
comments, and remove redundant additional_permissions block.
Update actions/checkout from v4 to v6.

Signed-off-by: Alejandro Mery <amery@apptly.co>

Author: amery

.github/workflows/claude.yml

@@ -20,13 +20,13 @@ jobs:
     runs-on: ubuntu-latest
     permissions:
       contents: read
-      pull-requests: read
-      issues: read
+      pull-requests: write
+      issues: write
       id-token: write
       actions: read
     steps:
       - name: Checkout repository
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
         with:
           fetch-depth: 1
 
@@ -35,5 +35,3 @@ jobs:
         uses: anthropics/claude-code-action@v1
         with:
           claude_code_oauth_token: ${{ secrets.CLAUDE_CODE_OAUTH_TOKEN }}
-          additional_permissions: |
-            actions: read