Pete Adventure News: emit seam, !news command, cold-start backfill

gogobee's game-side of Pete's push-based Adventure news feed. Emits
structured event *facts* (not prose) to Pete's ingest endpoint over a
durable queue; Pete owns voice/authoring/publishing.

- internal/peteclient: durable pete_emit_queue + retry sender; Fact
  payload; FEATURE_PETE_NEWS master switch.
- pete.go: emitFact enforces runtime kill-switch + per-player opt-out
  (anonymize, never drop); zone-clear + realm-first tiering; !news
  command (player optout/optin, admin on/off).
- bootstrap_pete_news.go: cold-start backfill replays deaths +
  single-holder achievements + zone realm-firsts, backdated + NoPush,
  idempotent, fires only once the seam is live; seeds news_realm_firsts.
- Emit sites: death, zone_first, rival_result, milestone, arrival.
- db.go: pete_emit_queue, news_optout (+opted_out_at), news_realm_firsts.

Unshipped. Deploy Pete first, then set FEATURE_PETE_NEWS + ingest env.

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

main.go

@@ -13,6 +13,7 @@ import (
 	"gogobee/internal/bot"
 	"gogobee/internal/db"
 	"gogobee/internal/dreamclient"
+	"gogobee/internal/peteclient"
 	"gogobee/internal/plugin"
 	"gogobee/internal/util"
 	"gogobee/internal/version"
@@ -55,6 +56,11 @@ func main() {
 	}
 	db.RecordStartup(version.Version, version.Commit)
 
+	// Pete adventure-news seam: wire the outbound fact client from the
+	// environment (no-op unless FEATURE_PETE_NEWS=true). The background sender
+	// is started once the run context exists (below).
+	peteclient.Init()
+
 	// Create Matrix session. AUTH_MODE selects the transport:
 	//   masdevice (default) — MAS OAuth device grant over /sync.
 	//   appservice          — as_token auth over Synapse transaction push.
@@ -97,6 +103,9 @@ func main() {
 		cancel()
 	}()
 
+	// Drain the Pete adventure-news emit queue in the background until shutdown.
+	peteclient.StartSender(ctx)
+
 	// Show the bot online from boot (appservice mode; no-op under masdevice, where
 	// /sync refreshes presence implicitly). Safe before the listener — outbound only.
 	sess.StartPresence(ctx)