Repair stage Typesense events schema and reindex

[tlongwell-block]

Context

Stage search is failing because the stage Typesense events collection appears to predate the channel_id facet field. Current buzz-search schema expects:

{"name": "channel_id", "type": "string", "facet": true, "optional": true}

When the relay pushes the expected channel_id filter, Typesense returns a per-result multi_search error:

{ "code": 400, "error": "Could not find a filter field named `channel_id` in the schema." }

Task

Repair/recreate the stage Typesense events collection so it includes the current schema, then reindex/backfill events.

Acceptance criteria

• Stage events collection schema includes channel_id as expected by buzz-search.
• Existing indexed documents are backfilled/reindexed with channel_id values, including the __global__ sentinel for global events.
• Stage relay search no longer receives Could not find a filter field named channel_id from Typesense.
• Global and single-channel /query search probes return HTTP 200.
• Decide whether ensure_collection should detect missing fields and fail loudly / repair automatically, or document the manual ops path for future schema drift.

Related

• PR Parse Typesense multi_search errors #1208 now only improves diagnostics by parsing Typesense per-result errors correctly; it intentionally does not work around the missing schema field.