fix(git): fail closed on pending operation replay

[Qiyuanqiii]

Summary

• distinguish completed idempotent replays from write-ahead intents that never received a terminal receipt
• fail incomplete local Git mutation replays closed and require repository reconciliation
• apply the same rule to remote Git and PR operations, where blind retry could duplicate an external side effect
• add regression coverage for stale local review failure and unavailable PR-client failure

Root cause

Both services persisted an intent before the side effect, but every matching operation-key replay returned success immediately. If execution, the remote API, or receipt persistence failed, the durable row remained incomplete and all later retries falsely looked successful with an empty receipt.

Recovery semantics

The service does not automatically rerun an incomplete intent because the original Git/API side effect may already have happened. It returns FAILED_PRECONDITION; the operator must reconcile observable state and then use a new operation key if a fresh action is appropriate. Completed records keep their existing idempotent replay behavior.

Verification

• go test -count=1 -v ./internal/application -run "TestGitMutationService|TestGitRemoteService"
• go test -count=1 ./internal/store ./internal/repository
• go vet ./internal/application
• git diff --check