Avoid reconnect countdown rerenders

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What Changed

• Replaced the WebSocket reconnect countdown's ticking React state with a ref-backed named hook that refreshes the existing toast directly.
• Added React Scan before/after recordings for the reconnect countdown scenario:
  • Before recording
  • After recording

Why

react-doctor flagged WebSocketConnectionSurface.tsx because nowMs was updated every second but the coordinator renders null. That caused unnecessary React rerenders solely to update toast text. The new hook keeps the countdown timer outside React render state while preserving the visible reconnect toast countdown.

React Doctor verification:

• Before: WebSocketConnectionSurface.tsx had 1 rerender-state-only-in-handlers warning for nowMs.
• After: 0 matching warnings.

UI Changes

No intentional UI behavior changes. The reconnect toast still updates its countdown; React Scan recordings above show the before/after run with React Scan enabled.

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

  

Note

Avoid re-renders during WebSocket reconnect countdown by updating toast directly

• Extracts a buildReconnectToast helper in WebSocketConnectionSurface.tsx to construct the reconnect toast payload.
• Adds a useReconnectToastCountdown hook that runs a 1s interval to call toastManager.update directly, keeping the countdown display current without triggering component re-renders.
• Removes the nowMs state and its associated effect from WebSocketConnectionCoordinator, eliminating per-second re-renders during reconnect waits.

^{Macroscope summarized 71777a1.}