fix(session): make replacement receipt reconciliation idempotent on Windows

[asdfqwerzxcc]

Closes #4368.

Summary

Makes pending replacement-receipt reconciliation idempotent after destination_exists or Windows preflight invalid_request. The reconciler re-captures both paths and accepts success only when final disk state proves it:

• pending absent and canonical destination present: another reconciler completed the move;
• both present with equal SHA-256: exact-unlink the captured pending receipt;
• pending only: preserve the original publish failure;
• both absent or unequal content: fail closed with a receipt-integrity error.

No invalid_request is ignored without state and hash verification.

Regression coverage

• another reconciler moves pending to destination before the result is observed;
• an identical destination already exists;
• destination hash conflict remains fail-closed;
• a genuine pending-only invalid_request remains a publish error.

Validation

• Reproduced and manually validated using an installed-package patch on Windows; session writes recovered after the preflight race.
• bunx tsc --noEmit -p packages/coding-agent/tsconfig.json passes.
• git diff --check passes.
• Focused Bun tests could not run on the authoring macOS host because the repository native addon is absent and Cargo is unavailable to build it. CI should provide the native test environment.

[Yeachan-Heo]

Superseded by maintainer PR #4373, rebased onto current dev and merged as 278f0a6b4745a8905248afc6c621088afaefe06d. Your original fix remains author-attributed in the landed history; thank you @asdfqwerzxcc for reproducing the Windows race and contributing the core reconciliation patch.