Show provider subagents in the subagents track (#2013)

* Add provider-owned subagent stream contract

* OpenCode provider: detect child sessions, attach adopted children to the hosting server, synthesize external turns

- Emit internal provider_child_session_detected / provider_session_deleted stream events from the global event stream (before the no-active-turn gate), including BFS hydration of existing descendants on subscribe
- Track child sessions in a registry mapping child session id -> hosting server url; resumeSession attaches via acquireExisting() so adopted children share the parent's server generation and keep receiving live events
- Synthesize external turns for adopted (externally driven) sessions so timeline, tool calls, and permission requests stream without a Paseo-initiated prompt
- Honor launchContext.env in resumeSession (acquireDedicated parity with createSession)
- Stop folding child tool parts into the parent's sub_agent action log; the parent row stays as a pointer

* Render provider subagents in workspace timelines

* fix provider subagent timeline reliability

* fix provider subagent lifecycle edge cases

* fix provider subagent event fidelity

* Fix provider subagent history fidelity

* Fix restored provider subagent state

* Fix provider subagent visibility edges

* Restore provider subagent timelines

* Page provider subagent history

* Forward subagent questions reliably

* fix(subagents): preserve OpenCode child context

* fix(subagents): harden provider timeline routing

* fix(subagents): preserve provider page continuity

* fix(subagents): retain live child prompts

---------

Co-authored-by: Omer <639682+omercnet@users.noreply.github.com>

packages/app/src/subagents/track-presentation.test.ts

@@ -1,13 +1,16 @@
 import { describe, expect, it } from "vitest";
-import type { SubagentRow } from "./select";
+import type { PaseoSubagentRow, SubagentRow } from "./select";
 import {
   buildSubagentRowPresentationData,
   formatHeaderLabel,
   resolveRowLabel,
 } from "./track-presentation";
 
-function row(overrides: Partial<SubagentRow> & Pick<SubagentRow, "id">): SubagentRow {
+function row(
+  overrides: Partial<PaseoSubagentRow> & Pick<PaseoSubagentRow, "id">,
+): PaseoSubagentRow {
   return {
+    kind: "paseo",
     id: overrides.id,
     provider: overrides.provider ?? "codex",
     title: overrides.title ?? `Agent ${overrides.id}`,
@@ -91,7 +94,9 @@ describe("resolveRowLabel", () => {
 
 describe("buildSubagentRowPresentationData", () => {
   it("namespaces the key with a subagent prefix", () => {
-    expect(buildSubagentRowPresentationData(row({ id: "child-a" })).key).toBe("subagent_child-a");
+    expect(buildSubagentRowPresentationData(row({ id: "child-a" })).key).toBe(
+      "paseo_subagent_child-a",
+    );
   });
 
   it("marks the row ready when the title resolves to a real label", () => {