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/workspace-tabs/identity.ts

@@ -21,6 +21,13 @@ export function normalizeWorkspaceTabTarget(
     const agentId = trimNonEmpty(value.agentId);
     return agentId ? { kind: "agent", agentId } : null;
   }
+  if (value.kind === "provider_subagent") {
+    const parentAgentId = trimNonEmpty(value.parentAgentId);
+    const subagentId = trimNonEmpty(value.subagentId);
+    return parentAgentId && subagentId
+      ? { kind: "provider_subagent", parentAgentId, subagentId }
+      : null;
+  }
   if (value.kind === "terminal") {
     const terminalId = trimNonEmpty(value.terminalId);
     return terminalId ? { kind: "terminal", terminalId } : null;
@@ -76,6 +83,9 @@ export function workspaceTabTargetsEqual(
   if (left.kind === "agent" && right.kind === "agent") {
     return left.agentId === right.agentId;
   }
+  if (left.kind === "provider_subagent" && right.kind === "provider_subagent") {
+    return left.parentAgentId === right.parentAgentId && left.subagentId === right.subagentId;
+  }
   if (left.kind === "terminal" && right.kind === "terminal") {
     return left.terminalId === right.terminalId;
   }
@@ -131,6 +141,9 @@ export function buildDeterministicWorkspaceTabId(target: WorkspaceTabTarget): st
   if (target.kind === "agent") {
     return `agent_${target.agentId}`;
   }
+  if (target.kind === "provider_subagent") {
+    return `provider_subagent_${target.parentAgentId.length}_${target.parentAgentId}_${target.subagentId.length}_${target.subagentId}`;
+  }
   if (target.kind === "terminal") {
     return `terminal_${target.terminalId}`;
   }