fix(web): terminal tells the shell its new width as soon as you release a resize drag

[t3dotgg]

After you drag the right-panel terminal divider, the terminal grid reflows at once, but the shell only learns the new width 150ms later. Typing in that window goes to a shell that still lays out the old width, and the caret can land inside the prompt (#12058).

The Ghostty surface now listens for pointer release on window. If a PTY resize is still waiting on the debounce, it fits once and sends the size right away. The debounce stays in place during the drag, so the prompt does not reprint on every pixel. This covers the panel divider, drawer height, split panes, and sidebar drags. Clicks with no pending resize do nothing. OS window resizes stay on the debounce.

Proof

• New surface.test.ts case: shrink the mount mid-drag, then release at a final width. It fails on main (no onResize at release) and passes with this fix (one call with the final grid, no repeat from the observer).
• Headless Chromium with the real surface and a real bash PTY, narrowing and widening drags:
  • main sends the final size about 152ms after release.
  • This branch sends it 1–3ms after release, exactly once.
• Fuzzed drags plus typing on bash 5.2 and 5.3 (40–150ms simulated latency): no caret errors on either branch. I could not reproduce the exact caret-in-prompt frame from the issue recording on main in this setup, so this PR removes the 150ms gap the triage identified. It is not proven against that exact recording.
• surface.test.ts and ThreadTerminalDrawer.permissions.test.tsx pass (76 tests). Web typecheck, lint, and format are clean.

Refs #12058

Reviewed with sol-loop: 1 round with GPT-6.1 Sol.

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[macroscopeapp]

Approvability

Verdict: Approved at 59685ef

Macroscope's review found this PR approvable — This is a narrowly scoped terminal resize bug fix that flushes the final PTY dimensions on pointer release while preserving debounced updates during dragging. The production change is isolated to the terminal surface and includes a focused regression test, with no defaults, schema, infrastructure, or static-analysis configuration changes.

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📥 Commits

Reviewing files that changed from the base of the PR and between f99b202 and 59685ef.

📒 Files selected for processing: 2

• apps/web/src/terminal/ghostty/surface.test.ts
• apps/web/src/terminal/ghostty/surface.ts

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📝 Walkthrough

Changes

Terminal resize settling

Layer / File(s)	Summary
Settle pending resize on pointer release apps/web/src/terminal/ghostty/surface.ts, apps/web/src/terminal/ghostty/surface.test.ts	The surface listens for window pointerup and pointercancel events. If a resize is pending, it refits, cancels the debounce, and reports the current grid dimensions. The test verifies that release reports the settled dimensions once and that later updates do not trigger another callback.

Priority: ⬇️ Low

Estimated code review effort: 2 (Simple) | ~10 minutes

Change: Bug fix · Severity of issue fixed: Low

Suggested reviewers: shivamhwp, stienswout

Merge Risk: ⚪ Minimal · up to 59685

No actionable merge-blocking risk is identified for the terminal resize change.

Pre-merge checks: 4

Passed checks: 4 passed

Check name	Status	Explanation
Linked Issues check		Issue [#12058] requires the right-panel terminal to recompute its grid, report new PTY dimensions, and reflow after a resize. surface.ts now handles window-level pointerup and pointercancel even…
Out of Scope Changes check		The changes are limited to terminal resize-release handling and its regression test. Window-level release handling supports the same drag-resize behavior for the panel, drawer, split panes, and sideba…
Title check		The title clearly and concisely describes the primary fix: sending the terminal's new width immediately after a resize drag ends.
Description check		The description covers the problem, implementation, scope, linked issue, limitations, focused verification, test results, and tooling. It is mostly complete, although it does not include explicit main…

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