On WSL2 with Windows drives mounted at /mnt/c, git snapshot operations
can take 30+ seconds due to the slow 9P filesystem bridge. The original
code sent TurnStarted *after* the snapshot, causing the UI's 30-second
dispatch watchdog to fire with 'Turn dispatch timed out; the engine may
have stopped' before the turn ever appeared to start.
This commit sends TurnStarted immediately before the snapshot, so the
UI shows progress while the snapshot runs in the background.
Chun Tse
29be2b18f7