-- 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);