feat: enrich stage foundation — provider config, env setup, schema fix

- Remove foreign key on run_status.source_id to support sentinel rows
  for tracking one-time pipeline steps (compile_candidates, compile_votes,
  merge, compare)
- Add stage-3-enrich/config.ts with all provider configurations,
  ALL_PROVIDERS ordered local-first, and validateProviderKey() for
  startup key checks
- Add .env.example with required API keys for OpenRouter and Anthropic
- Add pipeline:run script to package.json using --env-file .env
- Add .env to root .gitignore coverage for data-pipeline/.env

data-pipeline/db/schema.sql

@@ -41,16 +41,7 @@ CREATE TABLE IF NOT EXISTS cefr_source_votes (
 -- stage:  round1 | round2 | tiebreak
 -- status: pending | complete | needs_review | flagged
 
-CREATE TABLE IF NOT EXISTS run_status (
-  id         INTEGER PRIMARY KEY,
-  source_id  TEXT    NOT NULL REFERENCES synsets(source_id),
-  model_name TEXT    NOT NULL,
-  stage      TEXT    NOT NULL,
-  status     TEXT    NOT NULL,
-  created_at TEXT    NOT NULL DEFAULT (datetime('now')),
-  updated_at TEXT    NOT NULL DEFAULT (datetime('now')),
-  UNIQUE (source_id, model_name, stage)
-);
+
 
 -- ── Round 1 output ────────────────────────────────────────────────────────────
 -- One row per translation/language per model. Written atomically per record.