fix: stabilize Local Studio job detail rendering

[hyeokjun32]

Summary

• Preserved the selected Local Studio job across job list refreshes.
• Auto-selected the newly created Run job and kept its detail panel stable.
• Added a queued-job note so local mode clearly explains why Runtime metrics are not available yet.
• Added static and route tests for the job detail stability contract.

Validation

• poetry run python3 -m pytest tests/test_studio_routes.py -q
• poetry run python3 -m pytest -q
• Manual HTTP checks for /studio, static assets, run, jobs, import, compare, and Jetson helper endpoints

Impact

• Prevents the selected job detail UI from flashing or disappearing after Run/List refreshes.
• Makes queued local jobs easier to understand without adding worker, DB, queue, auth, upload, or SaaS behavior.

Notes

• Still local-first.
• Queued jobs remain queued until a worker/dev completion flow or Runtime result import supplies metrics.