fix: show the window after React's first commit

[Ernxst]

Harness: Claude Code
Agent: none
Model: anthropic/claude-opus-5-5

Task statements

1. Fix GPUIX presents an empty first frame and pumps AppKit late after opening a window #600: pump AppKit straight after init, commit React before the window's first present so the first frame shows content, and install the default menus after the second frame; keep it correct for every entry path and on Windows and Linux. (Working-directory and workflow instructions omitted.)

2. Changes 1 and 3 are already on main from fix: pump AppKit sooner and install default menus after the first frames #608. Make the approved zed change so macOS displayLayer: frames request presentation, as a fork commit on top of macOS windows start their display link and tab queries late, adding about 25 ms before the first frames #599's pin. Fix the empty first frame on Windows as well if it has one, and say why Linux is unchanged. (Working-directory and workflow instructions omitted.)

Closes #600.

GPUI shows a show: true window while it opens it, before React has committed, so the first frame a GPU-IX window presented was an empty scene. #608 already landed the issue's other two changes: pumping AppKit on the first tick, and installing the default menus after the second frame. This PR covers the first frame.

On macOS and Windows, init() now opens the window hidden, and the first tick()/tickIdle() shows it. render() commits before it starts the frame loop, so the tree is in place when the window appears:

 render()
   renderer.init()          // opens the window hidden
   flushSync(root.render)   // commits the tree
   startFrameLoop()
     tickIdle()
+      reveal the window      // presents the committed tree
       pump AppKit

• macOS: the reveal marks the view's layer for display, orders the window front, and displays the layer if AppKit didn't. GPUI then draws the committed tree and presents it with the Core Animation transaction that shows the window. gpui: show a window opened hidden with its current frame zed#4 makes GPUI's displayLayer: frame request presentation. Without it, GPUI's inactive-window throttle often dropped that frame, and the window showed the scene it had presented while hidden until the display link drew. The default menus now wait for the shown window's second frame; before, the hidden window's own frame counted as the first.
• Windows: GPUI showed the window during Window::new, before the root view existed. The window now opens hidden, and the reveal applies GPUI's pending placement through the new gpui_windows::show_window_opened_hidden (gpui: show a window opened hidden with its current frame zed#4), which keeps focus: false from activating it. A hidden window gets no WM_PAINT, so the first frame it presents is drawn after the commit.
• Linux: unchanged. GPUI's X11 and Wayland backends ignore show: false, so there is no hidden state to reveal from.
• activateWindow() before the first tick, such as from a mount effect, performs the pending reveal itself, focused, so the window keeps its first frame and deferred default menus. A window opened with show: false is unchanged: activateWindow() still reveals it. A root that throws during the first render terminates before the window is ever shown.

examples/first-frame.test.ts initialises a renderer, commits a tree, pumps once and counts the frames presented in that pump. It covers a focused window, focus: false, and a requestAnimationFrame loop started from an effect:

Case	main	GPU-IX change, zed unchanged	This PR
focused	0 presents	0 or 1 (throttled in some runs)	1
focus: false	0	0	1
rAF from an effect	0	0 or 1 (throttled in some runs)	1
focus: false + rAF	0	0	1

Default menus still install: the menu bar has the app menu (Services, Hide, Hide Others, Show All, Quit with ⌘Q) and a Window menu, and a posted Cmd+Q key event quits the app.

Startup timing, for information: examples/bench/hello-gpuix.tsx, 10 runs each alternating with main (ed9832d3b0) on the same Mac with nothing else building, medians from launch. Present times come from a temporary log in GPUI's present():

From launch to	main	This PR
first present (any scene)	186.0 ms, empty scene, window visible	177.5 ms, empty scene, window hidden
first present containing the tree	266.3 ms	205.0 ms
the fixture's second requestAnimationFrame	264.3–281.1 ms	280.3–284.1 ms

The tree reaches the screen about 61 ms sooner. It comes with the present that shows the window, not with the display link. The second-requestAnimationFrame marker is 3–16 ms later across two sessions of 10 runs each.

Risk: a custom host that calls createRenderer().init() now sees its window only at its first tick()/tickIdle(). The README and skills/gpuix say to commit before ticking. The Windows path is compiled and tested only by Windows CI. Reverting both commits restores the previous behaviour.

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