chore: update Claude model to opus-4-6 in CI workflows (anthropics#556)

## Summary
- Update all GitHub Actions workflows to use `claude-opus-4-6` model
- Enable explicit model selection in `claude-code-review.yml` and
`claude.yml` (previously commented out)
- Update model from `claude-opus-4-5` to `claude-opus-4-6` in
`build-and-publish.yml`

## Test plan
- [ ] Verify `build-and-publish.yml` workflow runs successfully with new
model
- [ ] Verify `claude-code-review.yml` workflow triggers and uses correct
model on PR review
- [ ] Verify `claude.yml` workflow triggers and uses correct model on
issue/PR mention

## Changelog
<!-- CHANGELOG:START -->
<!-- CHANGELOG:END -->

🤖 Generated with [Claude Code](https://claude.com/claude-code) (0%
1-shotted by claude-opus-4-6)

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

Author: ashwin-ant

.github/workflows/build-and-publish.yml

@@ -94,7 +94,7 @@ jobs:
           anthropic_api_key: ${{ secrets.ANTHROPIC_API_KEY }}
           github_token: ${{ secrets.GITHUB_TOKEN }}
           claude_args: |
-            --model claude-opus-4-5
+            --model claude-opus-4-6
             --allowedTools 'Bash(git add:*),Bash(git commit:*),Edit'
 
       - name: Push to main

.github/workflows/claude-code-review.yml

@@ -33,8 +33,7 @@ jobs:
       with:
         anthropic_api_key: ${{ secrets.ANTHROPIC_API_KEY }}
 
-        # Optional: Specify model (defaults to Claude Sonnet 4, uncomment for Claude Opus 4)
-        # claude_args: --model claude-opus-4-20250514
+        claude_args: --model claude-opus-4-6
 
         # Direct prompt for automated review (no @claude mention needed)
         prompt: |

.github/workflows/claude.yml

@@ -45,8 +45,7 @@ jobs:
         with:
           anthropic_api_key: ${{ secrets.ANTHROPIC_API_KEY }}
 
-          # Optional: Specify model (defaults to Claude Sonnet 4, uncomment for Claude Opus 4)
-          # claude_args: --model claude-opus-4-20250514
+          claude_args: --model claude-opus-4-6
 
           # Optional: Customize the trigger phrase (default: @claude)
           # trigger_phrase: "/claude"