feat(cli): show the active mcpctl project in prime-agent's footer

`/mcpctl` could switch projects but there was no way to see which one was
active without running a command. prime-agent exposes the same status-bar
channel the model name uses (`ctx.ui.setStatus`), so the switcher now
publishes `mcpctl:<project>` there.

Wired to `session_start`, which fires on startup *and* on every reload —
including the reload the switch itself triggers — so the footer tracks
settings.json without extra bookkeeping. Cleared when no project is mounted.

Also fixes `notify(..., 'success')`: the API only accepts info|warning|error.
Not a live bug (prime-agent falls through to the same showStatus path as
'info') but it fails a typecheck of the extension against the real
ExtensionAPI, which is how it was found.

The extension ships as a JSON-escaped string and is never compiled by our
build, so it was typechecked out-of-tree against
@earendil-works/pi-coding-agent's published types.

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

@@ -510,6 +510,24 @@ describe('config prime-agent', () => {
     expect(exceptionSafeRead(join(tmpDir, '.mcpctl-project'))).toBeNull();
   });
 
+  it('the installed switcher extension publishes the active project to the footer', async () => {
+    const settingsPath = join(tmpDir, 'settings.json');
+    const cmd = createConfigCommand(
+      { configDeps: { configDir: tmpDir }, log },
+      { client, credentialsDeps: { configDir: tmpDir }, log },
+    );
+    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');
+    // Footer status, refreshed on startup and on every reload (which is what
+    // the switch itself triggers) — the mcpctl equivalent of the model name.
+    expect(ext).toContain("pi.on('session_start'");
+    expect(ext).toContain('ctx.ui.setStatus(STATUS_KEY');
+    expect(ext).toContain('`mcpctl:${active}`');
+    // notify() only accepts info|warning|error — 'success' is not a valid type.
+    expect(ext).not.toContain("'success'");
+  });
+
   it('the installed switcher extension passes --skip-marker', async () => {
     const settingsPath = join(tmpDir, 'settings.json');
     const cmd = createConfigCommand(