ci: prevent duplicate workflow runs for xgopilot branches

Add !xgopilot/** exclusion pattern to all workflow trigger configurations,
matching the existing dependabot pattern. This ensures that xgopilot branches
only trigger CI checks on pull_request events, eliminating redundant push
event triggers.

Fixes #1340

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

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

.github/workflows/targets.yml

@@ -6,6 +6,7 @@ on:
     branches:
       - "**"
       - "!dependabot/**"
+      - "!xgopilot/**"
   pull_request:
     branches: ["**"]