docs(issue-17): lib_int.sh runs python3 from PATH (N3)

mam_int / mam_int_knob call `python3 -I` because the file is also sourced
without lib.sh and so without $PY. The header now says so, and that without
a python3 on PATH they print nothing (rc 127). The code is unchanged.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01HCGpJXhSZasJLU38ksDghe

.agents/skills/lib_int.sh

@@ -6,6 +6,8 @@
 #
 # Issue #17 item 4: the rule itself is lib_py/ints.py, which the loop runner
 # imports too (runner.py::_positive_int); these functions only call it.
+# They run `python3` from PATH (this file has no $PY when sourced alone):
+# without one, mam_int and mam_int_knob print nothing (rc 127).
 _MAM_INTS_PY="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)/lib_py/ints.py"
 
 # mam_int <value> <min>