Adv 2.0 L4d: pets dual-write pet_* off AdvCharacter to player_meta

Eight pet_* columns added to player_meta (flags packed into pet_flags_json).
PetState + load/upsert/backfill helpers; dual-writes wired at every pet
mutation site (arrival, naming, supply-shop unlock, babysit trickle,
morning defense, misty reactivation). Backfill idempotent, runs on Init.

L4 grep-empty exit criterion intentionally NOT met for adventure_pets.go:
helpers still take *AdventureCharacter because external callers (babysit,
scheduler, npcs, combat_bridge, combat_stats, dnd_sheet, arena, character)
read pet fields directly. Cross-file signature flip belongs after the
dual-write soak.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

internal/plugin/adventure_npcs.go

@@ -239,6 +239,7 @@ func (p *AdventurePlugin) resolveMisty(ctx MessageContext, char *AdventureCharac
 		if err := saveAdvCharacter(char); err != nil {
 			slog.Error("npc: failed to save misty buff", "user", ctx.Sender, "err", err)
 		}
+		_ = upsertPlayerMetaPetState(char.UserID, petStateFromAdvChar(char))
 
 		reply := mistyAcceptLines[rand.IntN(len(mistyAcceptLines))]