perf(query): allow writes during snapshot searches

[zhangzhenghao]

Summary

• pin immutable collection query snapshots so Query, MultiQuery, and GroupByQuery release the collection read lock before long-running search work
• keep segment runtimes alive with query/cache ownership until the last lease is released
• make Close and Destroy wait for active query leases and retry/report delayed runtime close errors
• capture schema in the same snapshot generation as documents and runtime indexes

This follows Alibaba zvec's separation between short collection-handle locking and stable segment ownership, implemented with pure-Go lifecycle management.

Tests

• go test ./... -count=1 -timeout=20m
• go test -race ./... -count=1 -timeout=30m
• go vet ./...
• concurrency and runtime lifecycle tests repeated with -count=20/-count=50
• git diff --check

Scope

This change addresses query/write lock contention and safe runtime reclamation. It does not change the on-disk format, writer serialization, or ANN algorithms.

[codecov]

Codecov Report

❌ Patch coverage is 92.36111% with 11 lines in your changes missing coverage. Please review.
✅ Project coverage is 82.69%. Comparing base (2e6c9a0) to head (f9d90d3).

Files with missing lines	Patch %	Lines
collection.go	91.85%	11 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #23      +/-   ##
==========================================
+ Coverage   82.65%   82.69%   +0.04%     
==========================================
  Files         140      140              
  Lines       27883    27983     +100     
==========================================
+ Hits        23046    23140      +94     
- Misses       4837     4843       +6     

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