docs: add Rust error handling best practices and fix wiki-sync GPG signing (#29)

Added comprehensive Rust error handling documentation to CLAUDE.md:
- Never use unwrap() in production code
- Use expect() for programmer errors with descriptive messages
- Use unwrap_or()/unwrap_or_else() for safe defaults
- Use match or ? operator for proper error handling
- Include code examples and verification commands

Fixed wiki-sync workflow to support GPG commit signing:
- Added crazy-max/ghaction-import-gpg@v6 action
- Configured git_commit_gpgsign to satisfy repository rules
- Requires GPG_PRIVATE_KEY and GPG_PASSPHRASE secrets

This resolves the "Commits must have verified signatures" error
that was causing wiki sync automation to fail.

Author: NormB

.github/workflows/wiki-sync.yml

@@ -98,6 +98,15 @@ jobs:
             echo "No wiki changes detected"
           fi
 
+      - name: Import GPG key for signing
+        if: steps.check_changes.outputs.changes == 'true'
+        uses: crazy-max/ghaction-import-gpg@v6
+        with:
+          gpg_private_key: ${{ secrets.GPG_PRIVATE_KEY }}
+          passphrase: ${{ secrets.GPG_PASSPHRASE }}
+          git_user_signingkey: true
+          git_commit_gpgsign: true
+
       - name: Create Pull Request for wiki changes
         if: steps.check_changes.outputs.changes == 'true'
         uses: peter-evans/create-pull-request@v6
@@ -135,6 +144,7 @@ jobs:
 
             **Note**: This is an automated PR created by the Wiki Sync workflow.
           labels: documentation, automated
+          signoff: true
 
       - name: Summary
         if: steps.check_changes.outputs.changes == 'true'