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/plugin/adventure.go

@@ -533,6 +533,8 @@ func (p *AdventurePlugin) dispatchCommand(ctx MessageContext) error {
 		return p.handleTreasuresCmd(ctx, strings.TrimSpace(strings.TrimPrefix(lower, "treasures")))
 	case lower == "vault" || strings.HasPrefix(lower, "vault "):
 		return p.handleVaultCmd(ctx, strings.TrimSpace(args[len("vault"):]))
+	case lower == "journal":
+		return p.handleJournalCmd(ctx)
 	}
 
 	return p.SendDM(ctx.Sender, "Unknown command. Type `!adventure help` to see available commands.")
@@ -564,6 +566,7 @@ const advHelpText = `**Adventure Commands**
 ` + "`!adventure recipes`" + ` — List crafting recipes known at your current Foraging level
 ` + "`!adventure mastery`" + ` — Per-slot equipment mastery progress and active bonus
 ` + "`!adventure treasures`" + ` — List your treasures · ` + "`treasures lock`" + ` to refuse swaps
+` + "`!adventure journal`" + ` — Read the campaign pages you've recovered
 ` + "`!hospital`" + ` — Visit St. Guildmore's Memorial Hospital (same-day revival when dead)
 ` + "`!thom`" + ` — Visit Thom Krooke (housing and loans)
 ` + "`!adventure help`" + ` — This message