fix(cli): wait for the current turn to finish before an auto-update restart

[kavish-19]

Fixes #994.

The bug

main() schedules checkForUpdates 100ms after spawning the binary. When it finds a newer version it stages the download and then unconditionally stops the running process to install it:

const stagedBinary = await stageBinary(latestVersion, getDownloadTargetKey(), { quiet: true })
runningProcess.removeListener('exit', exitListener)
await stopRunningProcess(runningProcess)   // SIGTERM, then SIGKILL after 5s

The wrapper has no way to know whether the user is mid-turn — it's a separate process that only sees the child's exit event, not its state. So a download that lands a few seconds into a session kills a turn that is still running, which is exactly what the reporter describes: "once the download finishes, the CLI automatically restarts, even if I'm in the middle of a session."

The fix

A small cross-process signal, in the spirit of the marker files terminal-watchdog.ts already uses for the same kind of wrapper/binary coordination:

• Binary side (cli/src/utils/run-activity-marker.ts): writes a marker file for the duration of a turn and removes it when idle or on exit. It subscribes once to the store's isChainInProgress, so every current and future site that toggles that flag is covered without touching any of them. Named by the process's own pid, which the wrapper already has from spawning it — no handshake needed.
• Wrapper side (cli/release-core/launcher.js): waitForRunIdle(pid) polls for that marker to clear, and checkForUpdates awaits it after staging and before stopping the process.

Bounded and best-effort in both directions, so it can only ever delay a restart, never prevent one:

• A missing marker — already idle, an older binary that predates this file, a process that died without cleaning up — resolves immediately and preserves today's restart-right-away behavior.
• A turn that never ends stops blocking the update after 10 minutes.

The staging download itself is unchanged and still happens up front; only the stop-and-swap waits.

Testing

New tests:

• Marker: writes while a turn is in progress, removes when idle, no-ops when the value doesn't actually change, and never stacks a duplicate exit handler.
• waitForRunIdle: returns immediately with no marker, waits and returns once the marker clears, and gives up at maxWaitMs without touching the marker.
• Extended the existing checkForUpdates source-order check to require the wait between staging and stopping.

Confirmed red against the unfixed code (all four new launcher assertions fail — waitForRunIdle doesn't exist) and green after.

bun test cli/src/__tests__/release/wrapper-safety.test.ts cli/src/utils/__tests__/run-activity-marker.test.ts
 23 pass / 0 fail

Also ran the full cli/src suite before and after: identical 34 pre-existing failures and 32 errors either way (they reproduce on unmodified main — an OSC 52 clipboard test plus missing @types/react-dom / tar in the local environment), with 6 new passing tests and no regressions. tsc --noEmit on the cli package reports nothing new in any touched file.