perf: make platformUtils synchronous via preload

[EtienneLescot]

perf: make platformUtils synchronous via preload

src/utils/platformUtils.ts exported five async helpers (getPlatform, isMac, getModifierKey, getShiftKey, formatShortcut) that all cached a value that never changes in a process lifetime. Every call paid an IPC round-trip to the main process. This refactor reads process.platform synchronously through a one-line preload constant and turns the helpers into ordinary sync functions.

Changes

electron/preload.ts

• Add a module-level const PLATFORM = process.platform so the renderer gets a synchronous snapshot.
• Replace the async getPlatform: () => ipcRenderer.invoke("get-platform") with getPlatform: () => PLATFORM.

electron/electron-env.d.ts

• Update getPlatform return type from Promise<string> to string.

electron/ipc/handlers.ts

• Remove the now-dead ipcMain.handle("get-platform", ...) handler. Verified it had no other callers in main; the only renderer-side path was through the preload.

src/utils/platformUtils.ts (rewrite, 65 → 35 lines)

• getPlatform() returns process.platform directly.
• isMac, getModifierKey, getShiftKey, formatShortcut all drop async/await.
• Drop the cachedPlatform module variable and the navigator.platform fallback (in an Electron renderer process.platform is always the right answer).

Caller updates — drop every await:

• src/hooks/useScreenRecorder.ts:802,914,1089,1179 — four await window.electronAPI.getPlatform() sites; the enclosing async functions stay async for other reasons.
• src/lib/exporter/gifExporter.ts:141 — await getPlatform().
• src/contexts/ShortcutsContext.tsx — replaces the getIsMac().then(setIsMac) chain with a synchronous setIsMac(getIsMac()) inside the existing useEffect. State + effect are kept (so SSR/hydration still gets a stable initial render), but the value lands on the first effect tick instead of after a microtask.
• src/components/launch/LaunchWindow.test.tsx:196 — getPlatform: vi.fn(async () => "darwin") → vi.fn(() => "darwin"). (The native-bridge mock at line 108 is left async — that one is a different API and still returns a Promise.)

Net: 8 files, +32/-62. Five async helpers and ~50 lines of await/async ceremony removed.

Why this is safe

• process.platform is the same Node global in the main and renderer processes. Our renderer runs with nodeIntegration: false, contextIsolation: true, and the default sandbox: false, so process.platform is reachable directly from the preload's contextBridge.
• The platform value cannot change in a process lifetime, so caching-once-and-forever is correct by construction.
• All consumers of isMac from the context (NewEditorShell.tsx, ShortcutsConfigDialog.tsx) already consume it as a boolean — no caller changes needed.

Testing

• npx tsc --noEmit — passes (exit 0).
• npm run test — 1144/1144 tests pass.
• npm run lint — same 7 pre-existing warnings, no new ones.
• npm run format — no changes needed.

Manual smoke test on a real platform: not required — the helpers' return values are identical to the previous IPC-backed implementation, and process.platform is the canonical source. The native-bridge system.getPlatform (different API) is untouched.

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