fix(tui): reset leaked mouse tracking on startup

[janah01]

Issue for this PR

Closes #18901

Type of change

• Bug fix
• New feature
• Refactor / code improvement
• Documentation

What does this PR do?

When the TUI is force-killed externally (taskkill /F on Windows, kill -9 on POSIX), for instance when installing OpenCode Desktop while OpenCode CLI is running, mouse tracking stays enabled in the terminal. The next opencode launch inherits this dirty state because the renderer starts from whatever baseline the terminal is already in.

This sends ?1000l ?1002l ?1003l ?1006l on startup to clear any leaked mouse modes before the renderer sets up its own. Disabling already-disabled modes is a safe no-op.

How did you verify your code works?

• Launch on Windows Terminal, taskkill /F /PID, relaunch — terminal is clean
• Normal exit (/exit) — no change in behavior
• Ctrl+C exit — no change in behavior

Screenshots / recordings

N/A — not a UI change, terminal state fix.
Screenshot of the issue:

Checklist

• I have tested my changes locally
• I have not included unrelated changes in this PR

[github-actions]

The following comment was made by an LLM, it may be inaccurate:

Based on my search results, I found two related PRs that address similar mouse tracking issues in the TUI:

1. PR fix(tui): disable mouse tracking on exit to prevent terminal corruption #11019 - "fix(tui): disable mouse tracking on exit to prevent terminal corruption"

   • fix(tui): disable mouse tracking on exit to prevent terminal corruption #11019
   • Related because it also fixes mouse tracking terminal state, but focuses on disabling on exit rather than reset on startup

2. PR fix: disable SGR mouse tracking on exit to prevent ASCII codes #6709 - "fix: disable SGR mouse tracking on exit to prevent ASCII codes"

   • fix: disable SGR mouse tracking on exit to prevent ASCII codes #6709
   • Related because it addresses SGR mouse tracking issues, though also focused on exit behavior

The current PR (18902) is complementary to these - it handles the startup side of the problem (resetting leaked modes from force-killed processes), while the previous PRs addressed the exit side. These could potentially be part of the same comprehensive fix for terminal mouse tracking state management.

[github-actions]

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