Keep wheel zoom inside the chart

[callumalpass]

What changed

• replace the React-delegated chart wheel handler with a native non-passive listener
• cancel Ctrl/Cmd+wheel before Chrome applies page magnification
• retain pointer-anchored Planner chart zoom
• leave ordinary wheel scrolling to the browser
• exercise Ctrl+wheel in the Chromium end-to-end test

Why

Chrome treats React's delegated wheel listener as passive. Planner's existing preventDefault() therefore changed the chart zoom level but could not stop Chrome from magnifying the entire application at the same time.

Impact

Ctrl/Cmd+wheel over the timeline now zooms only the Gantt chart. Normal vertical and horizontal wheel scrolling is unchanged.

Validation

• pnpm typecheck
• pnpm lint
• pnpm test — 37 tests passed
• pnpm test:e2e — 2 Chromium tests passed
• pnpm build