fix(tui): refresh screen correctly after Ctrl+Z resume

[Piping]

Issue for this PR

Closes #16327

Type of change

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

What does this PR do?

When opencode is suspended with Ctrl+Z, resized in the shell, and resumed with fg, the TUI could return with stale/misaligned characters because resize handling did not reliably run through the renderer's signal path.

This change makes resume explicitly trigger SIGWINCH (which @opentui/core listens to) and then performs staged repaint passes after resume. In practice this ensures terminal size is reconciled before final draw and removes the broken frame artifacts.

How did you verify your code works?

• Reproduced locally before fix:
  1. Open TUI
  2. Press Ctrl+Z
  3. Resize terminal
  4. fg
  5. Observe incomplete redraw / artifacts
• Verified locally after fix with the same steps: screen redraw is complete and stable.
• Push hook also ran workspace typecheck successfully.

Screenshots / recordings

Not attached (terminal-only behavior). I can add a short recording if needed.

Checklist

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

[github-actions]

Thanks for your contribution!

This PR doesn't have a linked issue. All PRs must reference an existing issue.

Please:

1. Open an issue describing the bug/feature (if one doesn't exist)
2. Add Fixes #<number> or Closes #<number> to this PR description

See CONTRIBUTING.md for details.

[github-actions]

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