feat(web+nomos): fix chat streaming reactivity, unified activity timeline, tool cards in chat

- fix(web): Svelte 5 identity-based reactivity broke text_delta streaming —
  immutable message objects in all three chat handlers so text streams live
- feat(web): streaming cursor + inline status indicator merged into message flow
- feat(web): expandable inline tool call cards in chat thread
- feat(web): merge Plan + Event log into one backbone Activity timeline —
  filled status nodes, branch stubs, auto-scroll follow mode, per-session
  activityLog, compact for the rail
- fix(nomos): add X-Accel-Buffering:no to /chat SSE (proxy buffering)
- fix(nomos): plan step auto-close SQL param bug (store.go)
- polish: timestamps, role labels, code copy button, table overflow, min
  window size, delete AgentIndicator/ActivityTimeline dead code

web/src/lib/stores/windows.ts

@@ -122,5 +122,5 @@ export function openTaskWindow(sessionId: string | null, title: string): void {
     wm.focus(id)
     return
   }
-  wm.open({ id, title, width: 900, height: 640 })
+  wm.open({ id, title, width: 900, height: 640, minWidth: 600, minHeight: 400 })
 }