feat: add title and description fields to capture grammar

Implement | prefix for titles and // separator for descriptions
across the full stack: parser, schema, API, CLI, and web frontend.

- Parser: line-aware extraction for |title, |title // desc,
  // leading desc, body // inline desc. URL-safe (skips :// lines).
  Modifiers (#tag, @time, ^card) extracted from all segments.
- Schema: ALTER TABLE migration adds title, description columns
- DB: Entity/EntityUpdate structs, all CRUD queries updated
- API: title/description on create/update/response, body validation
  relaxed (title-only entries valid)
- CLI: shows title as scan label when present
- Web: parseInput mirrors Go parser, list shows title, detail pane
  renders title + description with double-click inline editing
- Tests: 10 new cases (grammar, entity, API) — 71 total, all pass

internal/db/db.go

@@ -84,7 +84,14 @@ func (s *Store) migrate() error {
 		CREATE INDEX IF NOT EXISTS idx_entity_tags_tag
 			ON entity_tags(tag);
 	`)
-	return err
+	if err != nil {
+		return err
+	}
+
+	s.db.Exec(`ALTER TABLE entities ADD COLUMN title TEXT`)
+	s.db.Exec(`ALTER TABLE entities ADD COLUMN description TEXT`)
+
+	return nil
 }
 
 func DefaultPath() (string, error) {