perf(useRegistry): optimize unregister operations with deferred reindexing

[johnleider]

• Add deferred reindexing with indexDependentCount tracking to avoid O(n²) complexity
• Add offboard() method for batch unregistration with single reindex
• Optimize onboard() to batch cache invalidation and event emission
• Use collection.values() iterator directly in reindex() to avoid array allocation

Benchmark improvements:

• unregister with explicit values: 104x faster (59ms → 0.57ms for 1000 items)
• offboard with index values: 111x faster (deferred reindex)
• offboard with explicit values: 93x faster

[pkg-pr-new]

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commit: 7483cf4

[Copilot]

Pull request overview

This PR introduces significant performance optimizations to the useRegistry composable by implementing deferred reindexing with indexDependentCount tracking. The optimization reduces complexity from O(n²) to O(n) for batch unregistration operations by avoiding redundant reindexing after each deletion.

Key changes:

• Deferred reindexing system that only triggers when index-dependent values need updating
• New offboard() batch method for removing multiple tickets with a single reindex operation
• Partial reindexing optimization that only processes affected tickets from the dirty index onwards

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
packages/0/src/composables/useRegistry/index.ts	Implements deferred reindexing with indexDependentCount tracking, adds offboard() batch unregistration method, and optimizes reindex() for partial updates
packages/0/src/composables/useRegistry/index.bench.ts	Adds comprehensive benchmarks for the new optimization, including separate tests for explicit values and index values in register/unregister/onboard/offboard operations