fix(browser): stop webview NSView leak on close + tighten toolbar

[BunsDev]

Description

Two small fixes for the embedded browser pane.

Webview leak on pane close. BrowserView::close only persisted state and emitted PaneEvent::Close. With the default UndoClosedPanes feature flag the pane group keeps BrowserView alive in a shadow state instead of dropping it, so the Vec<Rc<RefCell<NativeBrowserWebView>>> survives, the wry::WebView survives, and its WKWebView NSView stays attached to the parent NSView — painting as a visible artifact of the browser content over the workspace after the pane is gone.

Fix: add NativeBrowserWebView::detach_native() which drops the wry::WebView (triggering wry's Drop, which calls removeFromSuperview) without touching desired_visible. BrowserView::close calls it for every webview. If the pane is restored via Cmd+Shift+T, set_bounds → attach_if_needed rebuilds the webview from pending_url on the next paint. Page state since closure is lost; URL is preserved.

Toolbar too tall. TOOLBAR_HEIGHT was 48pt around a 32pt URL bar — ~16pt of dead space that made the chrome look bulky next to neighboring panes. Tightened to 36pt (URL bar + 4pt total padding, 2pt each side).

Linked Issue

No linked issue — reported directly during manual testing of #74.

• The linked issue is labeled ready-to-spec or ready-to-implement.
• Where appropriate, screenshots or a short video of the implementation are included below (especially for user-visible or UI changes).

Testing

• cargo check -p warp-app --bin cast-codes --features gui → clean, 8 pre-existing warnings.

• Manually built and ran via ./script/run; reporter confirmed "browser closes clean" — no artifact remains after closing a browser pane.

• I have manually tested my changes locally with ./script/run

Screenshots / Videos

To add — before/after of toolbar height; close-pane recording showing no leftover content. The artifact bug is fully reproducible on main (open browser pane → close → see lingering webview content over workspace) and clean on this branch.

Agent Mode

• CastCodes Agent Mode - This PR was created via CastCodes Agent Mode

Out of scope

A third symptom reported alongside these — HTML in-page clicks dead inside the embedded webview (<select> dropdowns and in-page buttons all unresponsive) — is not fixed here. Root cause appears to be in warpui (GPUI fork) NSView hit-test routing: the parent canvas's hitTest:withEvent: likely returns self before subviews are tested, so AppKit never delivers events to the WKWebView. That needs framework-level work and deserves its own investigation/PR.

Co-Authored-By: Claude Opus 4.7 (1M context) noreply@anthropic.com

[Copilot]

Pull request overview

This PR addresses two UI issues in the embedded browser pane: it ensures native WKWebView views are detached on pane close to prevent macOS NSView artifacts when UndoClosedPanes keeps the pane alive, and it tightens the toolbar height to reduce excess vertical space.

Changes:

• Add NativeBrowserWebView::detach_native() to drop the underlying wry::WebView (detaching the NSView) while preserving intended visibility state.
• Invoke detach_native() for all tab webviews in BrowserView::close() before persisting state and emitting the close event.
• Reduce TOOLBAR_HEIGHT from 48pt to 36pt and update the surrounding sizing rationale comment.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
app/src/browser/webview_host.rs	Adds a detach_native() helper to explicitly drop the native webview so its NSView is removed immediately.
app/src/browser/browser_view.rs	Calls detach_native() on close to prevent lingering native views, and tightens toolbar height constant/commentary.

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