Phase 3: parse stored Compass pages into structured items

Turn the raw pages stored by Phase 2 into rows in the SQLite items table
(AGENTS.md §11 Phase 3, FR-3/FR-4/FR-5/FR-12).

- internal/parse: dependency-free HTML reader plus extractors for the ExtJS
  learning-task grid (subject, title, category, kind, due date, status), the
  home news feed (author, posted time, title, body) and the calendar week grid
  (day column + grid offset give the time; label gives title/room/teacher).
- internal/parse: fail loudly. A challenge page, login page, changed layout or
  unknown due-date format is an explicit error, never an empty day.
- FR-4: structure is parsed deterministically; importance is classified by an
  OmniRoute model (default openrouter/google/gemini-3.5-flash-lite) with a
  deterministic fallback. The classifier used is printed and recorded.
- internal/llm: small OpenAI-compatible OmniRoute client (handles SSE replies).
- internal/store: migration 002 adds source_page, importance and external_ref
  with a unique (child_id, source, type, external_ref) index; UpsertItems,
  CountItemsByType, SampleItems and ChildByName.
- cmd/school parse: reads var/raw/<child>/<run>, upserts items, records the scan
  row (ok=0 plus the error on failure) and prints counts and samples.
- scripts/parse-compass.sh and make parse run it in a one-off container against
  the service's own volume without restarting the service.
- docs/phase-3-parse-notes.md records the approach, the FR-4 decision and the
  known gaps.

Evidence on the live database: 56 rows for Harry (20 task, 1 message, 35 event).
Re-running the same raw pages inserts 0 and updates 56.

Co-Authored-By: Paperclip <noreply@paperclip.ing>

internal/store/migrations/002_items_parse.sql

@@ -0,0 +1,13 @@
+-- Migration 002 — Phase 3 parse columns (AGENTS.md §4 FR-4/FR-5, §11 Phase 3).
+--
+-- Every item records the page it came from (FR-5), a classification of
+-- importance (FR-4) and a stable external reference so re-parsing the same page
+-- updates a row instead of inserting a second one.
+
+ALTER TABLE items ADD COLUMN source_page  TEXT NOT NULL DEFAULT '';
+ALTER TABLE items ADD COLUMN importance   TEXT NOT NULL DEFAULT 'normal';
+ALTER TABLE items ADD COLUMN external_ref TEXT NOT NULL DEFAULT '';
+
+-- One row per real item: the same source item parsed twice maps to one row.
+CREATE UNIQUE INDEX IF NOT EXISTS idx_items_dedupe
+    ON items(child_id, source, type, external_ref);