test(runtime-host): validate Windows crash recovery

[jackwener]

Summary

Rebased landing of #2483 onto current main.

• Enable the killed Runtime Host recovery gate on Windows (no longer skip as POSIX process death)
• Use explicit IPC shutdown message for portable graceful Host teardown
• Close session/task-ledger stores before releasing root leases so Windows can remove SQLite files
• Refresh docs/windows-test-inventory.md (recounted: 19 backend-gap + 35 platform-contract = 54)

Rebase note

Inventory conflict with main only: removed the now-unskipped killed-Host row and recomputed classification counts.

Validation

• execution-host-queue tests: 9/9 pass (includes killed Host recovery)
• Prior CI on the fork PR also green including windows_baseline

Part of #2142.

Closes#2483.

Credits

@liugddx