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

internal/plugin/adventure.go

@@ -184,6 +184,7 @@ func (p *AdventurePlugin) Commands() []CommandDef {
 		{Name: "town", Description: "Town registry — civic pride, housing street, and the pet showcase", Usage: "!town", Category: "Games"},
 		{Name: "graveyard", Description: "Recent deaths across the guild", Usage: "!graveyard", Category: "Games"},
 		{Name: "rivals", Description: "Your rival duel record, or `!rivals board` for room-wide standings", Usage: "!rivals [board]", Category: "Games"},
+		{Name: "news", Description: "Pete's Adventure News — opt out of being named, or opt back in", Usage: "!news [optout|optin]", Category: "Games"},
 	}
 }
 
@@ -247,6 +248,10 @@ func (p *AdventurePlugin) Init() error {
 	// arrival roll. Both idempotent via JobCompleted gates.
 	bootstrapCasterSpellBackfill()
 	bootstrapGrantStarterPet()
+	// Pete adventure-news cold-start: replay the back-catalogue (realm-firsts,
+	// deaths, single-holder achievements) the first boot the seam is live, so
+	// launch doesn't open onto an empty section. One-shot, kept (see gap #7).
+	p.bootstrapPeteNewsBackfill()
 	// Phase R1 orphan-archive used to run here on every Init, but it
 	// over-archived: it treats any active dnd_zone_run row not linked to
 	// an active expedition as a legacy `!adventure dungeon` orphan, which
@@ -438,6 +443,9 @@ func (p *AdventurePlugin) OnMessage(ctx MessageContext) error {
 	if p.IsCommand(ctx.Body, "rivals") {
 		return p.handleRivalsTopCmd(ctx, p.GetArgs(ctx.Body, "rivals"))
 	}
+	if p.IsCommand(ctx.Body, "news") {
+		return p.handleNewsCmd(ctx)
+	}
 
 	// 1. Arena commands (work in rooms and DMs)
 	if p.IsCommand(ctx.Body, "bail") {