fix(subagents): keep the pushed footer status still, not a frozen spinner

Review caught an animation that cannot animate. ui.setStatus stores a
finished string and updateStatus only runs when the watched work changes,
so a spinner frame there freezes on whatever event wrote it last — a hung
UI is worse than an honest still marker. The strip owns the animated glyph
because it owns a render loop.

Also drops shared/ -> extensions/subagents/ internal import: shared code
must not depend on one extension's internals.

Refs #41

Author: tt-a1i

extensions/shared/activity-status.test.ts

@@ -1,6 +1,5 @@
 import assert from "node:assert/strict";
 import test from "node:test";
-import { SPINNER_INTERVAL_MS } from "../subagents/src/ui/transcript.ts";
 import {
   formatActivityStatus,
   hasActivity,
@@ -56,13 +55,12 @@ test("a settle without a timestamp is treated as unread", () => {
 
 test("status text names its own view command", () => {
   assert.equal(
-    formatActivityStatus(
-      identityTheme,
-      "subagents",
-      { running: 1, done: 2, failed: 0 },
-      0,
-    ),
-    "subagents: ⠋ 1 running · ✓ 2 done · /subagents to view",
+    formatActivityStatus(identityTheme, "subagents", {
+      running: 1,
+      done: 2,
+      failed: 0,
+    }),
+    "subagents: ● 1 running · ✓ 2 done · /subagents to view",
   );
   assert.equal(
     formatActivityStatus(identityTheme, "workflows", {
@@ -74,24 +72,24 @@ test("status text names its own view command", () => {
   );
 });
 
-test("running work shares the spinner frame; strip visibility owns the hint", () => {
+test("the pushed footer status uses a still marker; strip visibility owns the hint", () => {
   const counts = { running: 1, done: 0, failed: 0 };
+  // setStatus stores a finished string, so this line cannot animate: a spinner
+  // frame would freeze on whatever event happened to write it last.
   const visible = formatActivityStatus(
     identityTheme,
     "subagents",
     counts,
-    SPINNER_INTERVAL_MS, // frame 1
     true,
   );
-  assert.equal(visible, "subagents: ⠙ 1 running");
+  assert.equal(visible, "subagents: ● 1 running");
   assert.doesNotMatch(visible, /to view/);
 
   const hidden = formatActivityStatus(
     identityTheme,
     "subagents",
     counts,
-    SPINNER_INTERVAL_MS,
     false,
   );
-  assert.equal(hidden, "subagents: ⠙ 1 running · /subagents to view");
+  assert.equal(hidden, "subagents: ● 1 running · /subagents to view");
 });

extensions/shared/activity-status.ts

@@ -1,5 +1,11 @@
 import type { ExtensionContext } from "@earendil-works/pi-coding-agent";
-import { spinnerFrame } from "../subagents/src/ui/transcript.ts";
+
+/**
+ * Still marker for the push-based footer status. It deliberately does not
+ * import the subagent spinner: `shared/` must not depend on a single
+ * extension's internals, and a pushed string cannot animate anyway.
+ */
+const RUNNING_MARK = "●";
 
 type Theme = ExtensionContext["ui"]["theme"];
 
@@ -43,17 +49,23 @@ export function hasActivity(counts: ActivityCounts) {
   return counts.running + counts.done + counts.failed > 0;
 }
 
+/**
+ * `ui.setStatus` stores a finished string and is only called when the watched
+ * work changes, so this line is NOT re-evaluated per frame. A spinner here
+ * would freeze on whatever frame the last event happened to land on, which
+ * reads as a hung UI. The animated glyph belongs to the strip, which owns a
+ * render loop; the footer states the count with a still marker.
+ */
 export function formatActivityStatus(
   theme: Theme,
   label: "subagents" | "workflows",
   counts: ActivityCounts,
-  now: number = Date.now(),
   stripVisible = false,
 ) {
   const parts: string[] = [];
   if (counts.running > 0) {
     parts.push(
-      theme.fg("warning", `${spinnerFrame(now)} ${counts.running} running`),
+      theme.fg("warning", `${RUNNING_MARK} ${counts.running} running`),
     );
   }
   if (counts.done > 0) {

extensions/subagents/index.ts

@@ -393,13 +393,7 @@ export default function (pi: ExtensionAPI) {
     ui.setStatus(
       "subagents",
       hasActivity(counts)
-        ? formatActivityStatus(
-            ui.theme,
-            "subagents",
-            counts,
-            Date.now(),
-            widgetVisible,
-          )
+        ? formatActivityStatus(ui.theme, "subagents", counts, widgetVisible)
         : undefined,
     );
   };