Upgrade Claude model reference in CI/CD workflows (#63)

## Summary
Updates the Claude model reference used in GitHub Actions workflows to
ensure compatibility with the latest API specifications and improved
performance.

## Key Changes
- Updated model reference in the `create-pr.yml` workflow configuration
- Updated model reference in the `tag-release.yml` workflow
configuration
- Maintained existing workflow structure and functionality

## Key Accomplishments
- ✅ Ensures CI/CD workflows use the most current Claude model version
- ✅ Maintains backward compatibility with existing workflow triggers
- ✅ Preserves all existing workflow functionality and parameters

## Breaking Changes
None. This is a non-breaking update that only modifies internal model
references.

## Testing Notes
- Verify that PR creation workflows function correctly with the updated
model
- Confirm tag release automation continues to work as expected
- Monitor workflow execution logs for any model-related issues

## Infrastructure Considerations
- This change affects GitHub Actions workflow execution
- No additional dependencies or permissions required
- Workflows will utilize the updated model on next execution
- Consider monitoring initial workflow runs to ensure smooth transition

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

**Branch Info:**
- Source: `chore/upgrade-claude-cicd-model`
- Target: `main`
- Type: feature

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

Author: jfrench9

.github/workflows/create-pr.yml

@@ -210,7 +210,7 @@ jobs:
 
           # Create a proper JSON payload using jq to handle escaping
           PAYLOAD=$(jq -n \
-            --arg model "claude-sonnet-4-20250514" \
+            --arg model "${{ vars.CLAUDE_MODEL || 'claude-sonnet-4-6' }}" \
             --arg content "$PROMPT" \
             '{
               "model": $model,

.github/workflows/tag-release.yml

@@ -173,7 +173,7 @@ jobs:
 
           # Create a proper JSON payload using jq to handle escaping
           PAYLOAD=$(jq -n \
-            --arg model "claude-sonnet-4-20250514" \
+            --arg model "${{ vars.CLAUDE_MODEL || 'claude-sonnet-4-6' }}" \
             --arg content "$PROMPT" \
             '{
               "model": $model,