fix(desktop): re-assert zoom on display topology changes

[kaishi00]

What does this PR do?

Fixes a remaining trigger for the long-standing zoom reset bug (#60693): Chromium silently resets webContents zoom when the display topology changes — monitors going to sleep, waking with stagger, or being connected/disconnected.

These events fire on Electron's screen module, not on the BrowserWindow, so the existing window-level reassert in installZoomReassertOnWindowEvents (added in #66988) never runs. On multi-monitor setups with staggered wake (common on Windows), window-level resized/moved events may also arrive before all displays have settled, causing the persisted zoom to be applied and immediately overwritten by a later display change.

Root Cause

The existing zoom reassert covers three trigger categories:

Trigger	Where it fires	Covered by
Window resize, minimize/restore, cross-display move	BrowserWindow events	installZoomReassertOnWindowEvents (#66988)
Renderer load / reload / crash recovery	webContents.did-finish-load	#46429 / #61925
Display topology change (monitor sleep/wake/connect/disconnect)	screen module events	❌ Not covered → this PR

The codebase already uses this exact screen.on() pattern for the macOS wake indicator repositioning (main.ts:11835-11839), so this PR follows an established precedent.

Changes Made

• apps/desktop/electron/zoom.ts: Add installZoomReassertOnDisplayEvents(screen, win, reassert) — subscribes to display-metrics-changed, display-added, and display-removed on the screen module with a 300ms debounce (vs 100ms for window resize) to absorb staggered multi-monitor wake. Cleans up all listeners on window close.
• apps/desktop/electron/main.ts: Call the new function in wireCommonWindowHandlers alongside the existing window-level reassert, passing the already-imported screen from Electron.
• apps/desktop/electron/zoom.test.ts: 5 new tests covering: event wiring, debounce coalescing, destroyed-window skip, listener cleanup on close, and no-op guards.

How to Test

1. Set UI Scale to 125% in Settings
2. Let monitors sleep (or disconnect/reconnect a display)
3. Wake monitors — zoom stays at 125% instead of resetting to default
4. vitest run apps/desktop/electron/zoom.test.ts — all zoom tests pass

Verified on Windows 11 with a 3-monitor setup over 3 days of daily monitor sleep/wake cycles — zoom persisted correctly after the fix where it previously reset ~50% of the time.

Checklist

Code

• I've read the Contributing Guide
• My commit messages follow Conventional Commits
• I searched for existing PRs to make sure this isn't a duplicate
• My PR contains only changes related to this fix/feature (no unrelated commits)
• I've added tests for my changes (required for bug fixes)
• I've tested on my platform: Windows 11 (3-monitor setup, staggered wake)

Documentation & Housekeeping

• N/A — no config keys, architecture changes, or tool behavior changes

Technical Details

Why 300ms debounce (not 100ms)? Multi-monitor wake is staggered: display 1 wakes at T+0, display 2 at T+150ms, display 3 at T+250ms. Each wake fires display-metrics-changed. The existing 100ms window-event debounce is too short — a reassert at T+100ms gets overwritten by the display-2 wake at T+150ms. 300ms lets all monitors settle before re-applying the persisted zoom.

Why pass screen as a parameter instead of importing it? Matches the existing installZoomReassertOnWindowEvents pattern where platform is passed in rather than read from globals — keeps the function pure and testable without booting Electron.

Listener cleanup. Each call to wireCommonWindowHandlers (main window + each session window) registers 3 screen.on() listeners. Without cleanup on win.on('closed'), these would accumulate across session windows and leak stale window references. The closed handler calls screen.off() for all three events.

[teknium1]

Thanks for isolating the remaining display-topology path. Current main restores persisted zoom only through the BrowserWindow lifecycle hook and did-finish-load in apps/desktop/electron/main.ts:8690-8699; its helper has no screen event registration (apps/desktop/electron/zoom.ts:71-98).

PR commit b13ff3ebe72c75ff3fd123f613e5af99c23c1c79 adds the distinct Electron screen subscriptions, coalesces them with a trailing 300 ms debounce, and removes each listener when the associated chat window closes. The existing zoom: false helper-window exclusions remain intact because the wiring stays inside the existing if (zoom) branch. GitHub reports clean mergeability and passing desktop test/lint checks.

Automated hermes-sweeper review.