TUI renders with wrong dimensions after suspend/resume if terminal was resized while suspended

[aliou]

I have a working fix here, but not super confident of it as I can't tell if it has subtle side effects on other tui things. Opus issue summary below + Video repro

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Issue Summary

Problem:

When the user suspends pi with Ctrl+Z, resizes the terminal, then resumes with fg, the TUI renders with the old (pre-suspend) dimensions instead of the new terminal size.

Root Cause:

1. When process is suspended (SIGTSTP), Node.js cannot receive signals
2. SIGWINCH (window change signal) sent by OS during resize is lost
3. On resume, process.stdout.columns and process.stdout.rows still hold stale values
4. TUI renders with wrong dimensions, causing display corruption

Fix (two parts):

1. terminal.ts: In ProcessTerminal.start(), send SIGWINCH to ourselves to refresh cached dimensions:

   process.kill(process.pid, "SIGWINCH");

2. tui.ts: Add forceClear flag to ensure screen is cleared on resume even when previousWidth is reset to 0:

   • requestRender(true) sets forceClear = true
   • doRender() checks needsClear = widthChanged || forceClear and clears screen if true

[badlogic]

Cheers, should be fixed.