Confirm column mapping overrides for a matched segment

Stores confirmed column mapping overrides for a matched-subtype segment. Call this after reviewing the POST /v1/match/{id}/analyze response to correct any incorrect predictions. Sets mapping_confirmed: true so the platform skips its own analysis and uses these mappings directly.

column_mappings may be omitted entirely — the platform then re-runs column analysis on the currently active upload itself and accepts its own suggested mapping as-is (the same behavior as reviewing POST /v1/match/{id}/analyze and confirming without edits, in one call). This can return 409 FILE_NOT_YET_UPLOADED if the file hasn't finished uploading yet, or 422/400 on other analysis failures — pass column_mappings explicitly to skip re-analysis entirely.

If the segment was created or refreshed with hitl: true, the upload is still staged (not yet at the path that triggers automatic resolution) — this call also moves the staged file into place and starts identity resolution, which is why it can return 500 STAGING_COPY_FAILED if that move fails (the segment is left unchanged in that case; retry the call). Use POST /v1/segments/{id}/mappings/cancel instead to abort a staged upload without confirming. Requires 'creator' scope.