fix(app): give team-status-rail its own gray for zero-pane teams

app/src/App.css

@@ -664,6 +664,7 @@ body.resizing-row {
 .team-status-dot.status-working { background: #e0af68; }
 .team-status-dot.status-idle { background: var(--green); }
 .team-status-dot.status-unknown { background: var(--green); }
+.team-status-dot.status-empty { background: var(--muted); }
 .collapsed-team-status {
   width: 28px;
   padding: 2px;

app/src/agentStatus.test.ts

@@ -24,8 +24,12 @@ describe("applyStateChange", () => {
 });
 
 describe("aggregateTeamStatus", () => {
-  it("returns unknown for an empty set", () => {
-    expect(aggregateTeamStatus([])).toBe("unknown");
+  it("returns empty for a team with no panes", () => {
+    expect(aggregateTeamStatus([])).toBe("empty");
+  });
+
+  it("returns unknown for a pane whose agent type isn't recognized", () => {
+    expect(aggregateTeamStatus([status("unknown")])).toBe("unknown");
   });
 
   it("lets one blocked pane beat every other state", () => {

app/src/agentStatus.ts

@@ -1,13 +1,22 @@
 export type RawState = "idle" | "working" | "blocked" | "unknown";
 export type PaneStatus = { state: RawState };
 export type PaneStatusMap = Record<string, PaneStatus>;
+// A team's aggregate is either one of the pane states, or "empty" — no
+// agent has ever been started for that team. "unknown" (a pane exists but
+// classify() doesn't recognize its agent type) is deliberately a distinct
+// value from "empty" (no pane exists at all): #406 made "unknown" render
+// green like idle, since an unhandled type isn't an anomaly, but a team
+// nobody has started anything in isn't "idle" — it should read as inert
+// gray instead of implying live, healthy agents.
+export type TeamAggregateState = RawState | "empty";
 
 export function applyStateChange(map: PaneStatusMap, paneId: string, newState: RawState): PaneStatusMap {
   if (map[paneId]?.state === newState) return map;
   return { ...map, [paneId]: { state: newState } };
 }
 
-export function aggregateTeamStatus(statuses: PaneStatus[]): RawState {
+export function aggregateTeamStatus(statuses: PaneStatus[]): TeamAggregateState {
+  if (statuses.length === 0) return "empty";
   const priority: Record<RawState, number> = {
     blocked: 3,
     working: 2,