test(resolve): isolate tier2 temp databases

[sunerpy]

Fixes the Windows-only CI race seen in main run 33439224974: parallel Tier 2 tests reused the same fixture name and could receive the same coarse wall-clock timestamp, opening one SQLite file concurrently. Add a process-local atomic nonce plus a fixed-clock uniqueness regression test. Local targeted tests, make ci, and the pre-push gate all pass. No product, golden, Skill, extraction-version, or release impact.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

@@           Coverage Diff           @@
##             main     #264   +/-   ##
=======================================
  Coverage   95.36%   95.37%           
=======================================
  Files         144      144           
  Lines       84347    84347           
=======================================
+ Hits        80441    80443    +2     
+ Misses       3906     3904    -2     

see 1 file with indirect coverage changes

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