adventure: stay out of the room when TwinBee already said it

gogobee announces treasure finds, duels, mischief contracts and the
Siege to the games room in TwinBee's voice, and files the same moments
here as facts. Both land in the same room, so the realm heard every one
of them twice, in two voices, minutes apart.

Hold those types back from Matrix. They are stored and published on the
site exactly as before, and the push alerts still fire; only the live
priority beat and the digest sweep skip them, retired against the digest
the same way a no_push backfill is. Types with no room announce behind
them (zone clears, arrivals, deaths, milestones) are untouched and stay
Pete's to report.

room_silent_types overrides the default set; an explicit empty list
turns the suppression off.

internal/web/server.go

@@ -69,6 +69,7 @@ type Server struct {
 	pushHTTP       *http.Client                  // SSRF-guarded client for Web Push delivery; built lazily by pushClient()
 	adv            config.AdventureConfig        // gogobee adventure-news seam
 	advPost        PriorityPoster                // posts priority adventure beats to Matrix; nil = web-only
+	roomSilent     map[string]bool               // event types TwinBee announces itself: site yes, Matrix never
 	channels       []Channel                     // live sections: the catalogue minus anything gated off (adventure)
 
 	// Daily-rotated salt for the privacy-preserving unique-visitor estimate.
@@ -144,7 +145,7 @@ func New(cfg config.WebConfig, sources []config.SourceConfig, postingEnabled boo
 		live = append(live, ch)
 	}
 
-	s := &Server{cfg: cfg, sources: infos, postingEnabled: postingEnabled, tpls: tpls, adminSubs: adminSubs, adv: adv, advPost: advPost, channels: live, hub: newGamesHub(), tableLocks: newStripedLocks(), tableGames: []tableGame{holdemTable{}, unoTable{}}}
+	s := &Server{cfg: cfg, sources: infos, postingEnabled: postingEnabled, tpls: tpls, adminSubs: adminSubs, adv: adv, advPost: advPost, roomSilent: adv.RoomSilentSet(), channels: live, hub: newGamesHub(), tableLocks: newStripedLocks(), tableGames: []tableGame{holdemTable{}, unoTable{}}}
 
 	// Optional OIDC sign-in (Authentik). Discovery is a network call; if the
 	// provider is unreachable at boot we log and serve anonymously rather than