refactor(prime-agent): drop the widget fallback, keep the tray status

With prime-agent-extension-status.patch in place the tray renders
ctx.ui.setStatus() next to the model name, which is what a status line should
be. The widget was a workaround for its absence and was never a substitute:
widgetContainerBelow sits in the fullscreen *scroll* list, not the dock, so it
scrolled away with the transcript, and with both set the project name appeared
twice.

The startup retries stay: resetExtensionUI() clears extension statuses just as
it cleared widgets, so the value set during session_start is still wiped before
it can be seen.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017BMXdb2qZbPSh8Q7XpTyjB

src/cli/tests/commands/prime-agent.test.ts

@@ -537,12 +537,12 @@ describe('config prime-agent', () => {
     await cmd.parseAsync(['prime-agent', '--project', 'ha', '-o', settingsPath, '--skip-skills', '--token', 'mcpctl_pat_x'], { from: 'user' });
 
     const ext = readFileSync(join(tmpDir, 'extensions', 'mcpctl-switch.ts'), 'utf-8');
-    // prime-agent stores extension statuses but never renders them, so a
-    // setStatus-only indicator is invisible there. Widgets are rendered.
-    expect(ext).toContain('ctx.ui.setWidget(STATUS_KEY');
-    expect(ext).toContain("placement: 'belowEditor'");
-    // Still set the status: pi's footer does render it.
+    // Both hosts render statuses next to the model name (pi in its footer,
+    // prime-agent in the tray — the latter via prime-agent-extension-status.patch).
     expect(ext).toContain('ctx.ui.setStatus(STATUS_KEY');
+    // The widget was a workaround for the unpatched tray; it scrolled away with
+    // the transcript, so it is not a status line and must not come back.
+    expect(ext).not.toContain('setWidget');
     // prime-agent emits session_start only from reload(), never at startup, so
     // a session_start-only indicator stays blank until the first switch.
     expect(ext).toContain("pi.on('turn_start'");