feat(tui): batch event delivery

[jlongster]

Summary

• queue backend events and flush pending delivery every 10 ms
• emit each queued snapshot in one Solid batch while preserving FIFO order
• cancel pending delivery and discard queued events during provider cleanup
• remove the characterization test accidentally included in the preceding refactor PR

Testing

• bun test test/cli/tui/use-event.test.tsx
• bun typecheck