Advisory source health: review flags, never auto-deactivate

- Add source health columns (last_success_at, last_error_at, last_error,
  consecutive_failures, review_flag, review_reason) via SCHEMA + migration.
- poll_source maintains them: success resets the failure streak and records the
  success time; failure increments it and stores the latest error.
- review_sources() flags active sources that are stale, repeatedly failing,
  low-acceptance, duplicate-heavy, or doom-skewed (high cortisol/ragebait) over
  a recent window. It is purely advisory: it sets review_flag/review_reason and
  never changes the active column (human stays in the loop), clearing the flag
  when a source recovers.
- CLI review-sources; cycle runs it as a final step (--no-review to skip);
  source-report shows a review line for flagged feeds.
- Tests: healthy/failing/stale/low-acceptance/recovery and never-deactivates.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

goodnews/feeds.py

@@ -108,6 +108,15 @@ def poll_source(conn: sqlite3.Connection, source: sqlite3.Row) -> dict:
             """,
             (seen, inserted, duplicate, run_id),
         )
+        # A clean poll resets the failure streak and records the success time.
+        conn.execute(
+            """
+            UPDATE sources
+            SET last_success_at = CURRENT_TIMESTAMP, consecutive_failures = 0
+            WHERE id = ?
+            """,
+            (source["id"],),
+        )
         conn.commit()
         return {"status": "ok", "seen": seen, "inserted": inserted, "duplicate": duplicate}
     except Exception as exc:
@@ -124,6 +133,17 @@ def poll_source(conn: sqlite3.Connection, source: sqlite3.Row) -> dict:
             """,
             (seen, inserted, duplicate, str(exc), run_id),
         )
+        # Track the failure streak and latest error for advisory review flags.
+        conn.execute(
+            """
+            UPDATE sources
+            SET consecutive_failures = consecutive_failures + 1,
+                last_error_at = CURRENT_TIMESTAMP,
+                last_error = ?
+            WHERE id = ?
+            """,
+            (str(exc), source["id"]),
+        )
         conn.commit()
         return {
             "status": "failed",