fix(ats): unblock Windows memory setup after ATSv2 durability fix

[AetherAI3]

Unblocks the Windows aether agent create ATS Atlas resume path after ATSv2 #442 merged.

• vendored bridge uses writable descriptors for native fsync on Windows
• source receipt pins the merged ATSv2 commit ecdbc5c296f28f2331aea4e031c459f1171b99ea
• Agent reports safe actionable memory-engine errors instead of collapsing them to a generic receipt mismatch
• adds focused coverage

Local verification: npm run ats:check, npm run typecheck, python3 -m py_compile packages/ats-skills/python/bridge.py, and 45/45 ats_agent tests pass.