feat: sync universal schema and sdk updates

research.md

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+# Research: Subagents
+
+Summary of subagent support across providers based on current agent schemas and docs.
+
+OpenCode
+- Schema includes `Part` variants with `type = "subtask"` and fields like `agent`, `prompt`, and `description`.
+- These parts are emitted via `message.part.updated`, which can be used to render subagent activity.
+
+Codex
+- Schema includes `SessionSource` with a `subagent` variant (e.g., review/compact), attached to `Thread.source`.
+- This indicates the origin of a thread, not active subagent status updates in the event stream.
+
+Claude
+- CLI schema does not expose subagent events.
+- The Task tool supports `subagent_type`, but it is not represented as a structured event; it may be inferred only from tool usage output.
+
+Amp
+- Schema has no subagent event types.
+- Permission rules include `context: "subagent"` and `delegate` actions, but no event stream for subagent status.
+
+Current universal behavior
+- Subagent activity is normalized into the standard message/tool flow; no dedicated subagent fields yet.