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/protocol/src/client-capabilities.ts

@@ -11,6 +11,9 @@ export const CLIENT_CAPS = {
   // Old clients use a strict TerminalState schema and would reject the extra fields.
   // Drop the gate (always send the flags) when floor >= v0.1.88.
   terminalReflowableSnapshot: "terminal_reflowable_snapshot",
+  // COMPAT(providerSubagents): added in v0.1.107. The daemon emits provider-owned
+  // child descriptors and timelines only to clients that understand the new messages.
+  providerSubagents: "provider_subagents",
   browserHost: "browser_host",
 } as const;