ao update skips rebuild when dist is stale at the current commit #2057

Summary

ao update (git / source installs) only rebuilds when git fetch advances the local commit. If the compiled output (dist/) is out of sync with src/ at the same commit, the script prints Already on latest version and skips the rebuild — so the running binary keeps executing stale compiled code.

How it happens

The rebuild is gated purely on the SHA advancing:

if [ "$local_sha" = "$remote_sha" ]; then
  printf 'Already on latest version.\n'   # ← skips pnpm install + build
else
  git pull ... && pnpm install && pnpm build ...
fi

So dist/ can be stale at HEAD via:

• a manual git pull before ao update (HEAD already matches remote → no rebuild)
• a branch switch
• an interrupted previous build (SHA advanced but the build never finished; re-running sees a matching SHA → no rebuild)
• a manual pnpm clean

Impact

Source / npm link installs (install method git) end up running whatever was last compiled. Seen in practice: a fix that exists in src/ throws at runtime because dist/ predates it (e.g. a session-restore change still throwing the pre-fix error). Registry installs (npm / pnpm / bun-global) are unaffected — they ship prebuilt dist/.

Proposed fix

Gate the rebuild on whether dist/ is in sync with HEAD, not on the SHA advancing:

• record the built commit in a gitignored marker (node_modules/.ao-build-sha), written only after a fully successful build + launcher refresh
• rebuild when the marker ≠ HEAD, the build output is missing, or --force-rebuild is passed
• add ao update --force-rebuild as an explicit escape hatch

Mirror the change in the PowerShell port and wire --force-rebuild through update.ts.