N3/P6d: a party where every member can see the dungeon

Every ownership lookup in the adventure module keys on a user id, and a
party member owns neither the expedition row nor the zone run. So each
player-facing read quietly told them they were not playing.

Rewire them. Reads a member should see resolve through activeExpeditionFor
/ activeZoneRunFor. Leader-only actions answer with copy that names the
leader instead of denying the expedition. Three busy-guards had to start
refusing a member outright: !zone enter, !expedition start and !sell all
keyed on the sender's own row, so a seated member could open a private
dungeon, outfit a rival expedition, or run a shop from the boss room.

Four things the rewire itself exposed:

!resources looks like a read but seed-persists harvest nodes, and
saveHarvestNodes rewrites the entire region_state blob — kills, event
gates, temporal stack — last-write-wins. Reaching it as a member would
revert the leader's walk from a stale snapshot. Persist only for the owner;
seedRoomNodes is pure, so a member re-derives the same nodes.

!zone taunt moves the party's shared mood, which is intended and safe:
applyMoodEvent lands an atomic delta. Its neighbour applyMoodDecayIfStale
writes an absolute gm_mood from the caller's snapshot, and every command
takes the *sender's* lock — a member running it against the leader's run
holds the wrong mutex. The owner check now lives on that function.

A seat outlives status='active'. releaseParty deliberately skips the
seven-day 'extracting' limbo, so the roster persists while
activeExpeditionFor goes blind — long enough for a member to open a run
that wins every lookup once the leader !resumes. seatedExpeditionFor spans
both statuses; it is what the busy-guards ask.

!expedition run was still member-blind. It is the same walk as !zone
advance, reached by its other name.

isPartyMember replaces `run != nil && !isLeader`: activeZoneRunFor reports
isLeader=false for a player with no run anywhere, so the bare test sends a
solo player to go ask their leader.

Golden byte-identical; solo T1 expedition clears end-to-end.

internal/plugin/dnd_zone_cmd_graph.go

@@ -163,7 +163,7 @@ func (p *AdventurePlugin) zoneCmdGo(ctx MessageContext, rest string) error {
 	}
 	if !isLeader {
 		// The fork is one choice for one party, and the run is the leader's row.
-		return p.SendDM(ctx.Sender, "Your party leader picks the path. `!map` to see where you're standing.")
+		return p.SendDM(ctx.Sender, msgLeaderPicksPath)
 	}
 	if cs, _ := activeCombatSessionFor(ctx.Sender); cs != nil {
 		return p.SendDM(ctx.Sender, "⚔️ Finish your fight first — `!attack` or `!flee`.")