Create a new branch (forked session) from a snapshot.
Strategy: Copy the snapshot's JSONL to the Claude project directory
with a new session ID, update sessions-index.json, then resume.
This is more reliable than --fork-session because we control file placement.
Create a new branch (forked session) from a snapshot.
Strategy: Copy the snapshot's JSONL to the Claude project directory with a new session ID, update sessions-index.json, then resume. This is more reliable than --fork-session because we control file placement.