`--intent` silently dropped when a run was already registered by the post-receive hook

Environment: no-mistakes v1.31.2, macOS, gate runs registered via the git push post-receive hook.

What we observed (2026-07-04, controlled docs-only canary): the crew pushed a branch — the post-receive hook registered the gate run — and then invoked no-mistakes with --intent "<text>". The intent did not appear to take effect on the already-registered run: no error, no warning, behavior as if the flag was dropped.

Expected: either attach the provided intent to the existing registered run, or fail/warn loudly that it's being ignored — silent dropping means the operator believes an intent constraint is active when it isn't (we use intents to scope what a gate run is allowed to do, so a silently dropped one is a guardrail that isn't there).

Caveat: observed once during a broader incident-audit day; we haven't built a minimal repro yet. Filing early because the silent-drop shape seemed worth flagging — happy to gather more detail if this isn't already known/intended.