feat: add Pi subagent scheduler and child runtime

tests/unit/pi-event-projector.test.ts

@@ -58,6 +58,52 @@ function apply(
 }
 
 describe('Pi event projector', () => {
+  it('projects only subagent.v1 details and never exposes unknown raw details', async () => {
+    const projector = new PiEventProjector({ createId: () => 'unused' });
+    let snapshot = emptySnapshot();
+    snapshot.nodes.push({
+      kind: 'tool', id: 'tool-subagent', toolCallId: 'call-subagent', toolName: 'subagent',
+      title: 'subagent', inputText: '{}', status: 'running', output: [],
+    });
+    snapshot = apply(snapshot, await projector.project(snapshot, {
+      type: 'tool_execution_update',
+      toolCallId: 'call-subagent',
+      partialResult: {
+        content: [],
+        details: {
+          schema: 'subagent.v1', dispatchId: 'dispatch-a', mode: 'parallel',
+          tasks: [{
+            taskId: 'task-a', agentId: 'agent-a', toolProfile: 'read-only',
+            status: 'complete', summary: 'done', usage: { inputTokens: 3, outputTokens: 5 },
+          }],
+        },
+      },
+    }));
+    expect(snapshot.nodes).toContainEqual(expect.objectContaining({
+      kind: 'subagent', id: 'subagent:dispatch-a', runId: 'run-a',
+      details: expect.objectContaining({ schema: 'subagent.v1' }),
+    }));
+    expect(snapshot.nodes).toContainEqual(expect.objectContaining({
+      kind: 'tool', id: 'tool-subagent',
+      details: expect.objectContaining({ dispatchId: 'dispatch-a' }),
+    }));
+
+    snapshot.nodes.push({
+      kind: 'tool', id: 'tool-unknown', toolCallId: 'call-unknown', toolName: 'subagent',
+      title: 'subagent', inputText: '{}', status: 'running', output: [],
+    });
+    snapshot = apply(snapshot, await projector.project(snapshot, {
+      type: 'tool_execution_end',
+      toolCallId: 'call-unknown', isError: false,
+      result: { details: { schema: 'subagent.v2', raw: 'RAW_SECRET_DETAILS' } },
+    }));
+    expect(JSON.stringify(snapshot)).not.toContain('RAW_SECRET_DETAILS');
+    expect(snapshot.nodes).toContainEqual(expect.objectContaining({
+      kind: 'tool', id: 'tool-unknown',
+      output: [expect.objectContaining({ text: 'Subagent details are unavailable for this version.' })],
+    }));
+  });
+
   it('keeps one assistant UI identity while content-index deltas become an authoritative message', async () => {
     const projector = new PiEventProjector({
       createId: () => 'assistant-ui-a',