fix(conclude): publish request log on terminal reconcile + make idempotent

[sbalabanov]

Summary

The conclude controller reconciles each request in a concluded batch to the batch's terminal state (Landed / Error / Cancelled) but did not emit a corresponding RequestLog entry, leaving the request lifecycle log without a terminal record. Peer controllers (start, score, cancel) already publish to the log topic on their transitions; this brings conclude in line.

The per-request loop is also made idempotent under at-least-once redelivery:

• Already in target terminal state → skip the CAS but still publish the log. The log queue dedupes on (request_id, status), so a prior delivery that completed the state update but failed before publishing the log gets its log emitted on retry, recorded exactly once.
• In a different terminal state (a racing writer reached terminal first) → skip both the CAS and the log publish; the other writer owns the terminal log entry for the state it wrote. Recorded via a terminal_state_divergence metric and a warning log.
• Not terminal → CAS to target state, then publish log.

Test plan

• bazel test //submitqueue/orchestrator/controller/conclude:conclude_test passes
• Added test case: idempotent retry — request already Landed, no UpdateState mocked (gomock would fail if called), publisher still expected
• Added test case: divergent terminal state — request already Cancelled for a Succeeded batch; neither UpdateState nor publish allowed
• Existing cases updated to expect log publish on the happy path
• make gazelle clean (picks up new submitqueue/core/request dep)
• make fmt clean

🤖 Generated with Claude Code

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