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

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

packages/app/e2e/helpers/rewind-flow.ts

@@ -154,6 +154,10 @@ export async function launchAgent(input: {
   provider: RewindFlowProvider;
   cwd: string;
   mode: "full-access";
+  providerConfig?: {
+    model?: string;
+    extra?: { codex?: { features?: { multi_agent_v2?: boolean } } };
+  };
 }): Promise<AgentHandle> {
   execFileSync("git", ["init", "-b", "main"], { cwd: input.cwd, stdio: "ignore" });
   execFileSync("git", ["config", "user.email", "paseo-test@example.com"], {
@@ -180,6 +184,7 @@ export async function launchAgent(input: {
   }
   const agent = await client.createAgent({
     ...fullAccessConfig(input.provider),
+    ...input.providerConfig,
     cwd: input.cwd,
     workspaceId: createdWorkspace.workspace.id,
     title: `rewind-flow-${input.provider}-${randomUUID()}`,