Task: todo 19a — notification-gate peek + read-only HTTP API
Date: 2026-09-01

Files created/modified:
- crates/news-server/src/gate.rs (refactored: shared decide(), new peek(), tests)
- crates/news-server/src/api/mod.rs (register config + stories modules)
- crates/news-server/src/api/config.rs (new GET /api/config endpoint + tests)
- crates/news-server/src/api/stories.rs (new GET /api/stories endpoint)
- crates/news-server/src/api/stories/tests.rs (new tests)
- crates/news-server/src/main.rs (wire /api/config and /api/stories routers)

Verification commands
---------------------

1. Formatting
   $ cargo fmt --all --check
   Result: clean

2. Clippy
   $ cargo clippy --workspace --all-targets -- -D warnings
   Result: clean

3. Workspace tests
   $ cargo test --workspace
   Result: passed (83 tests total)
   - news-cli: 2 passed
   - news-core: 18 passed
   - news-ingest: 4 passed
   - news-server: 41 passed (up from 33 in task 18)
   - news-store: 22 passed

4. Build
   $ cargo build --workspace --bins
   Result: finished successfully

Implementation notes
--------------------
- NotificationGate::peek is side-effect-free: clones the token bucket, refills
  in memory only, calls the shared decide() logic, and never writes
  notification_log or decrements budget.tokens.
- Shared decision logic lives in a private decide() method used by both
  evaluate_with_mode and peek, guaranteeing identical Notify/Digest/Suppress
  outcomes.
- GET /api/stories queries story_clusters joined to raw_items for the canonical
  item, recomputes relevance (RelevanceScorer) and importance
  (ImportanceScorer) per request, derives percentile ranks from
  percentile_stats over a 7-day window, calls gate.peek, and returns a JSON
  array of story rows with decision/reason/last_notification_lane.
- GET /api/config returns the current in-memory NewsConfig as JSON.
- Both endpoints are read-only: no notification_log rows are written and the
  gate token budget is unchanged after a request.

Known divergences from plan wording
-----------------------------------
- Percentile ranks are computed with a direct SQL query on percentile_stats
  rather than through PercentileTracker, because PercentileTracker exposes no
  rank API and news-store is frozen for this task.