fix: Prefer runtime version over package manager after upgrade

[finxo]

Pull Request

📝 Summary

Fixes autoupdate version detection to prefer the runtime version over package manager metadata after successful upgrades. This ensures the correct version is reported when the runtime has been updated but package manager metadata hasn't refreshed yet.

🔧 Changes Made

• Added _get_installed_version_runtime() helper to query version from current Python runtime
• Modified update_core() to prefer runtime version over pipx/pip metadata after successful upgrades
• Added unit test covering the runtime version preference scenario

🧪 Testing

• Unit tests added/updated (poetry run pytest)
• All tests passing (make test)
• Manual testing with titan-dev

Added test_update_core_prefers_runtime_version_after_pipx_upgrade which verifies that when pipx upgrade succeeds, the runtime version (0.3.0) is reported instead of the stale pipx metadata version (0.2.0).

📊 Logs

• No new log events

✅ Checklist

• Self-review done
• Follows the project's logging rules (no secrets, no content in logs)
• New and existing tests pass
• Documentation updated if needed