Is plan state preserved when resuming via `SessionStore` + `materialize_resume_session()`?

## Question

When using `SessionStore` with `materialize_resume_session()`, the temp `CLAUDE_CONFIG_DIR` includes transcripts, auth files, and subagent transcripts — but we don't see plan files (`{config_dir}/plans/*.md`) being materialized.

If the agent was in plan mode (`EnterPlanMode`) when the session was interrupted and later resumes via `--resume` with a materialized temp dir:

1. **Does the CLI reconstruct plan state from the transcript?** The transcript contains the `EnterPlanMode` tool calls and plan content — is that sufficient for the CLI to restore plan context, or does it need the `.md` file on disk?

2. **More broadly, is the transcript + auth files + subagent transcripts the complete set of state needed for a full resume?** Or are there other session-related files under `CLAUDE_CONFIG_DIR` that `materialize_resume_session()` should include?

## Context

We're using `SessionStore` in a multi-pod deployment where the resuming pod doesn't have the original `CLAUDE_CONFIG_DIR`. The only state available is what `materialize_resume_session()` writes to the temp dir.

## Environment

- `claude-agent-sdk` v0.1.66
- Python 3.14