Fix medium-severity audit issues in core query and React bindings

[ConsoleTVs]

Summary

Resolves 7 medium-severity issues identified during the codebase audit. These fixes address event listener leaks, race conditions, error handling gaps, and cross-environment compatibility.

Core Query Engine (query.ts)

• Wrapped BroadcastChannel.postMessage() in try-catch to prevent DataCloneError crashes when emitting non-cloneable data
• Added AbortSignal support to once(), enabling stream() and sequence() generators to clean up event listeners when consumers break out of iteration
• Added abort race condition guard in trigger() — checks controller.signal.aborted after fetch resolves to prevent writing stale data to cache after an abort() call
• Captured broadcast reference at call time in subscribeBroadcast() to prevent stale closure if configure() replaces the broadcast channel
• Wrapped await item.item in forget() with try-catch so rejected promises don't prevent remaining keys from being forgotten

Type Definitions (options.ts)

• Updated OnceFunction type to accept optional AbortSignal parameter (non-breaking — parameter is optional)

React Bindings (QueryProvider.tsx)

• Added typeof BroadcastChannel guard in useEffect for edge runtime compatibility

Tests (query.test.ts)

• Fixed tautological assertions in cache access test — was comparing items to itself instead of itemsCache