The Pi backend hardcoded `--tools read,bash,edit,write,grep,find,ls` in
buildPiArgs. Pi's SDK treats --tools as a restrictive allowlist: only the
listed tools pass through `_refreshToolRegistry()`, silently filtering
out any user-installed extension tools registered via `pi.registerTool()`.
Omitting --tools makes Pi's `allowedToolNames` undefined, so the
`isAllowedTool()` filter becomes a no-op and all tools — built-in and
extension — are available. This matches Pi's standalone behavior.
Users who want to restrict tools can still pass --tools via custom_args
(it is not in piBlockedArgs).
Closes#2379
702c48209b