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 88.38710% with 18 lines in your changes missing coverage. Please review.
✅ Project coverage is 61.54%. Comparing base (07b981b) to head (f2bfd4f).

Files with missing lines	Patch %	Lines
collection.go	87.67%	10 Missing and 8 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #23      +/-   ##
==========================================
+ Coverage   61.44%   61.54%   +0.09%     
==========================================
  Files         150      150              
  Lines       40358    40462     +104     
==========================================
+ Hits        24799    24901     +102     
- Misses      12344    12346       +2     
  Partials     3215     3215              

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