feat(app): give composer track pills a segment per state

A mixed fan-out used to collapse the pill to its single most urgent
state, so a red dot beside "1 failed" over a child that was still
working read as the whole fan-out having stopped. Every state present
now gets its own mark and count, in the sidebar's status-group order.

packages/app/src/i18n/resources/en.ts

@@ -1674,7 +1674,7 @@ export const en = {
     title: "Subagents",
     pillLabelOne: "1 subagent",
     pillLabelMany: "{{count}} subagents",
-    pillLabelRunning: "{{count}} running",
+    pillLabelWorking: "{{count}} working",
     pillLabelFailed: "{{count}} failed",
     pillLabelNeedsInputOne: "1 needs input",
     pillLabelNeedsInputMany: "{{count}} need input",