Avoid WebSocket coordinator countdown rerenders

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What Changed

• Removed countdown nowMs React state from WebSocketConnectionCoordinator so the reconnect toast countdown no longer re-renders the coordinator every second.
• Moved the coordinator side effects into a named hook, useWebSocketConnectionCoordinatorEffects, and refreshed the reconnect toast via an effect event instead of render-driving state.
• Added react-scan before/after evidence artifacts:
  • docs/performance/react-scan-websocket-coordinator-before.webm
  • docs/performance/react-scan-websocket-coordinator-after.webm
  • docs/performance/react-scan-websocket-coordinator-before.json
  • docs/performance/react-scan-websocket-coordinator-after.json

Why

React Doctor flagged WebSocketConnectionSurface.tsx with rerender-state-only-in-handlers: nowMs was updated for countdown bookkeeping but never rendered by the component. In the reconnect waiting state this caused avoidable coordinator update renders once per second. The toast still updates on the same cadence, but the coordinator no longer needs to re-render for those ticks.

React-scan/Profiler capture summary over the same ~5.5s reconnect countdown harness:

• Before: 9 coordinator renders, 8 update renders.
• After: 2 coordinator renders, 1 update render.

UI Changes

No product UI behavior change intended. The committed .webm files are before/after screen recordings with react-scan enabled for the reconnect countdown harness.

Checklist

• This PR is small and focused
• I explained what changed and why
• I included before/after screenshots for any UI changes
• I included a video for animation/interaction changes

Validation:

• bun fmt
• bun lint
• bun typecheck
• bunx --bun react-doctor@latest . --diff main --verbose --json --offline --fail-on none

  

Note

Avoid 1s interval re-renders in WebSocketConnectionCoordinator

• Extracts coordinator side-effect logic into a new useWebSocketConnectionCoordinatorEffects hook in WebSocketConnectionSurface.tsx, removing nowMs state and its interval-driven updates.
• The periodic toast sync for the 'waiting' reconnect phase now calls a syncConnectionToast callback directly on a timer instead of updating React state, eliminating 1s re-renders on the coordinator component.
• Performance before/after captures are included in docs/performance/ to document the improvement.

^{Macroscope summarized f9a634d.}