This PR depends on [#31296](https://github.com/openai/codex/pull/31296)
for the canonical-to-legacy event mappings.
## Description
This PR makes the v1 and v2 wait paths emit canonical
`TurnItem::CollabAgentToolCall` lifecycle instead of
`CollabWaitingBegin` / `CollabWaitingEnd` directly.
Both paths already used the same legacy waiting events before this PR.
The v1 item carries receiver metadata and final agent statuses for its
target agents; v2 waits for mailbox activity rather than specific
agents, so it keeps those fields empty, matching the existing v2 legacy
payload.
App-server v2 consumes the canonical item directly and ignores the
mapped legacy wait events.
## Why
Wait is separate from the other collab tools because it is multi-target
and has distinct timeout/status behavior. Keeping it last also lets this
PR remove the old helper that only existed to shape legacy wait status
entries in core.
## What changed
- Emit canonical collab wait items from both v1 and v2 wait handlers.
- Preserve receiver metadata and agent status snapshots on completed
wait items.
- Remove the old core helper for building legacy wait status entries.
## Follow-up
The next stack PR, [#30188](https://github.com/openai/codex/pull/30188),
writes canonical `TurnItem` values to paginated rollout files.
Owen Lin
6b4882528e