Adds p.source_channel to the SELECT and surfaces it on each event.
Migration v22 populated the column with enum values: telegram, agent,
maintenance, unknown, github. Timeline UI needs this to show per-event
provenance (2340 telegram, 698 agent, 102 maintenance, 11 unknown, 1 github).
Nulls fall back to "unknown" — only 0 rows currently null, but the
fallback is defensive for future inserts before backfill runs.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Serves contribution events from pipeline.db. Classifies PRs as
create/enrich/challenge, normalizes contributors, derives summaries
from branch names when descriptions are empty. Hot sort uses
challenge*3 + enrich*2 + signal / hours^1.5 decay from event time.
Domain and contributor filters, pagination (limit/offset).
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
