feat(web-ui): live terminal output panel

[SurviveM]

Requirement

Add collapsible terminal panel at the bottom of Web UI. WebSocket streams real-time stdout/stderr from commands like codexmate codex / codexmate run. Support pause, clear, and search within output.

Verification

1. Open Web UI -> click terminal panel -> run codexmate codex "hello" -> see real-time output streaming
2. Click pause -> output freezes -> click resume -> streaming continues
3. Type in search box -> matching lines highlighted in output

[ymkiux]

This feature (live terminal output panel) is not in the current optimization plan. The terminal-related code has been removed from this PR. Will revisit in a future iteration.