adventure: tell Pete who else is on the expedition

Party seats ride the roster detail, beside the supply and threat numbers the
same expedition already publishes. Leader first, the hireling named without a
token he has no board row for, and an opted-out player's seat kept and
anonymised — dropping it would make a party of three read as a pair while the
burn rate and enemy scaling beside it still felt three bodies.

The board itself was wrong about this: it resolved an expedition with a lookup
keyed on dnd_expedition.user_id, which is blind to members, so for the whole
life of N3 parties a seated player has shown as idle in town while standing in
a dungeon.

Pets also send the engine's XP threshold for their current level band, so the
web can draw progress without keeping a copy of a curve that would drift.

internal/peteclient/client.go

@@ -284,6 +284,30 @@ type RosterDetail struct {
 	ThreatLevel int        `json:"threat_level,omitempty"`
 	Room        string     `json:"room,omitempty"`
 	Map         *RosterMap `json:"map,omitempty"`
+	// Party is who else is on this expedition, leader first. Absent for a solo
+	// run — a party of one is not a party, and the page should say nothing rather
+	// than draw a roster with a single chair in it.
+	Party []PartySeatView `json:"party,omitempty"`
+}
+
+// PartySeatView is one body on a shared expedition, as the public page may see
+// it. Kind is what the seat *is*, which the game keeps carefully separate:
+// "leader" owns the expedition row everyone else references, "member" is another
+// player, "companion" is the hired NPC (Pete) who fights but has no mailbox and
+// no loot.
+//
+// Name/Token are the same pair the board and the Siege muster use. The opt-out
+// rule here is the Siege *contributor* rule, not the realm-occupant rule: an
+// opted-out player's seat is anonymised (kept, with no name and no token) rather
+// than deleted. A party of three that renders as two is a false statement about
+// the run — the supply burn, the enemy scaling and the loot split all felt three
+// bodies — whereas an unnamed seat says only that somebody else was there, which
+// the zone line on this same page already implies.
+type PartySeatView struct {
+	Kind  string `json:"kind"` // leader|member|companion
+	Name  string `json:"name,omitempty"`
+	Token string `json:"token,omitempty"` // empty: opted out, or a companion (no board row)
+	Level int    `json:"level,omitempty"`
 }
 
 // RosterMap is the fog-of-war cut of an adventurer's zone graph: every node
@@ -788,11 +812,19 @@ type HouseView struct {
 }
 
 // PetView is one pet slot.
+//
+// XP and XPNeeded are both in **centi-XP** — the engine's own unit, a hundredth
+// of a point, because a pet earns 1.5 XP per action and the ledger is an int.
+// Pete divides by 100 to show it and does no other arithmetic on either number:
+// the curve behind XPNeeded is petXPToNextLevel's, per level band, and it is not
+// Pete's business to know it. XPNeeded is 0 at the level cap, which is the only
+// signal that there is nothing left to fill.
 type PetView struct {
 	Type      string `json:"type"`
 	Name      string `json:"name"`
 	Level     int    `json:"level"`
 	XP        int    `json:"xp,omitempty"`
+	XPNeeded  int    `json:"xp_needed,omitempty"` // 0 = at the level cap
 	ArmorTier int    `json:"armor_tier,omitempty"`
 }