Patch Probe Suite Membership

Replace this probe's EXPLICIT suite memberships. Body: { suite_ids: [<id>, ...] } # the full new explicit-membership list

Suites that gain the probe get it appended to explicit_probe_ids; suites that lose it get it removed. Tag-query memberships are NOT touched — those are a property of the suite's tag_query and the probe's tags, edited elsewhere.

Returns the same shape as GET /probes/{id}/suite-membership so the UI can render the post-save state in one round-trip.