fix: dispose() race condition when release() is in-flight

[koistya]

Summary

• Fix race condition where dispose() returned null when called while release() was awaiting backend
• Handle synchronous throws from backend.release() to prevent state getting stuck at "disposing"
• Add runtime validation to acquireHandle() for misconfigured backends/mocks

Changes

common/disposable.ts

• Track pendingRelease promise so dispose() can wait for in-flight release() operations
• Wrap backend.release() call to handle synchronous throws
• Validate decorated result methods in acquireHandle()

Tests Added

Test	Coverage
dispose() during in-flight release()	Waits for release to complete
dispose() during failing release()	Waits even when release throws
Synchronous backend throw	State transitions to "disposed" correctly
Undecorated backend result	Throws descriptive error

[codecov]

Codecov Report

❌ Patch coverage is 60.00000% with 16 lines in your changes missing coverage. Please review.
✅ Project coverage is 76.37%. Comparing base (d29ec05) to head (2881f90).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
common/disposable.ts	60.00%	16 Missing ⚠️

❌ Your patch status has failed because the patch coverage (60.00%) is below the target coverage (77.00%). You can increase the patch coverage or adjust the target coverage.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #26      +/-   ##
==========================================
+ Coverage   75.88%   76.37%   +0.49%     
==========================================
  Files          42       42              
  Lines        2658     2688      +30     
==========================================
+ Hits         2017     2053      +36     
+ Misses        641      635       -6     

Flag	Coverage Δ
contracts-firestore	47.05% <2.50%> (-0.91%)	⬇️
contracts-postgres	43.02% <2.50%> (-0.79%)	⬇️
contracts-redis	40.21% <2.50%> (-0.75%)	⬇️
e2e	59.40% <30.76%> (-0.31%)	⬇️
unit	64.37% <100.00%> (+1.37%)	⬆️

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Files with missing lines	Coverage Δ
common/auto-lock.ts	78.64% <ø> (+2.87%)	⬆️
common/disposable.ts	68.06% <60.00%> (+4.96%)	⬆️

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