This PR adds an experimental persist_extended_history bool flag to app-server thread APIs so rollout logs can retain a richer set of EventMsgs for non-lossy Thread > Turn > ThreadItems reconstruction (i.e. on thread/resume).

Motivation

Today, our rollout recorder only persists a small subset (e.g. user message, reasoning, assistant message) of EventMsg types, dropping a good number (like command exec, file change, etc.) that are important for reconstructing full item history for thread/resume, thread/read, and thread/fork.

Some clients want to be able to resume a thread without lossiness. This lossiness is primarily a UI thing, since what the model sees are ResponseItem and not EventMsg.

Approach

This change introduces an opt-in persist_full_history flag to preserve those events when you start/resume/fork a thread (defaults to false).

This is done by adding an EventPersistenceMode to the rollout recorder:

• Limited (existing behavior, default)
• Extended (new opt-in behavior)

In Extended mode, persist additional EventMsg variants needed for non-lossy app-server ThreadItem reconstruction. We now store the following ThreadItems that we didn't before:

• web search
• command execution
• patch/file changes
• MCP tool calls
• image view calls
• collab tool outcomes
• context compaction
• review mode enter/exit

For command executions in particular, we truncate the output using the existing truncate_text from core to store an upper bound of 10,000 bytes, which is also the default value for truncating tool outputs shown to the model. This keeps the size of the rollout file and command execution items returned over the wire reasonable.

And we also persist EventMsg::Error which we can now map back to the Turn's status and populates the Turn's error metadata.

Updates to EventMsgs

To truly make thread/resume non-lossy, we also needed to persist the status on EventMsg::CommandExecutionEndEvent and EventMsg::PatchApplyEndEvent. Previously it was not obvious whether a command failed or was declined (similar for apply_patch). These EventMsgs were never persisted before so I made it a required field.