N5/D1a: journal pages — the Hollow King campaign collectible

First slice of the N5 story layer. Adds a 24-page serialized campaign
threaded through the zones as collectible journal pages.

- Storage: one journal_pages INTEGER bitmask on player_meta (bit i ==
  page i+1). DEFAULT 0 is correct for every existing row, so no bootstrap.
  Grants are an atomic bitwise-OR (INSERT ... ON CONFLICT DO UPDATE SET
  journal_pages = journal_pages | excluded.journal_pages) so a page found
  mid-expedition can't be lost to a stale character save. Journal pages
  are therefore grant-only + overlay-read, never in the bulk upsert.
- Drop seam: elite kills roll a page (22%, tunable) in dropZoneLoot,
  gated on isElite — bosses get epilogues (D1b), not pages. Not on
  SimulateCombat's path, so TestCombatCharacterization is byte-identical.
- Viewer: !adventure journal renders found pages in story order with runs
  of missing pages collapsed to a single "…".
- Catalog + bitmask helpers + render live in the new
  adventure_flavor_campaign.go; the pages are in-world found artifacts,
  not TwinBee's voice.

Golden byte-identical; go test ./... green (incl. a real-DB round-trip
that pins the atomic OR + overlay read).

Claude-Session: https://claude.ai/code/session_017mEwUmmS7aQTP2NQXj6rUa

internal/db/db.go

@@ -378,6 +378,14 @@ func runMigrations(d *sql.DB) error {
 		`ALTER TABLE player_meta ADD COLUMN pet2_armor_tier INTEGER NOT NULL DEFAULT 0`,
 		`ALTER TABLE player_meta ADD COLUMN pet2_flags_json TEXT NOT NULL DEFAULT '{}'`,
 		`ALTER TABLE player_meta ADD COLUMN pet2_level_10_date TEXT NOT NULL DEFAULT ''`,
+		// N5/D1 the Hollow King campaign (gogobee_engagement_plan.md §D1). Found
+		// journal pages are a bitmask (bit i == page i+1 discovered), granted one at
+		// a time from elite kills and secret rooms. A single INTEGER rather than a
+		// rows table: pages are static content, only found/not-found is per-player,
+		// and grants are an atomic bitwise-OR so a page can't be lost to a stale
+		// character save. DEFAULT 0 == "no pages found", correct for every
+		// pre-existing row, so no bootstrap backfill.
+		`ALTER TABLE player_meta ADD COLUMN journal_pages INTEGER NOT NULL DEFAULT 0`,
 	}
 	for _, stmt := range columnMigrations {
 		if _, err := d.Exec(stmt); err != nil {