call-with-tool-timeout wraps tool execution with sb-ext:with-timeout
using per-tool timeout from *tool-timeouts*. On timeout returns
(:status :error :message "Timed out after Ns"). Wired into
action-tool-execute before the funcall. Timeout result detected and
propagated as :tool-error.
- core-act: call-with-tool-timeout fn, wired into action-tool-execute
- Act tests: +3 (timeout enforcement test)
- Core: 88/88
