fix(issue-26): the wrapper reads .mam.env through the Python loader's parser, never source

- lib_py/delegation/envfile.py (stdlib only) holds the one set of rules:
  comments and blank lines skipped, key and value stripped, one matching
  quote pair removed, no shell interpretation, keys must match
  ^[A-Za-z_][A-Za-z0-9_]*$ (bad or `=`-less lines warn with the line
  number, never the value).
- mqtt_common._parse_env_file delegates to envfile.apply.
- The delegate-job wrapper runs envfile.py --shell by path and evals the
  shlex-quoted exports; values never reach a command line. The environment
  now wins over the file in both loaders.
- .mam.env.example: commented assignments no longer use $HOME, which the
  parser keeps literally.

The shell parsed the env file in one place only (wrapper :38), not three.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

.agents/skills/multi-agent-mux-delegate-job/multi-agent-mux-delegate-job

@@ -34,8 +34,12 @@ if [[ -z "$TARGET_ENV" ]]; then
   fi
 fi
 
+# Issue #26: parsed by envfile.py (the Python loader's rules; environment wins),
+# never sourced. Values come back as shlex-quoted exports over the pipe.
 if [[ -n "$TARGET_ENV" && -f "$TARGET_ENV" ]]; then
-  set -a; source "$TARGET_ENV"; set +a
+  _env_exports="$("${DELEGATE_JOB_PYTHON:-python3}" -I "$SCRIPT_DIR/../lib_py/delegation/envfile.py" --shell "$TARGET_ENV")" \
+    || { echo "ERROR: cannot read $TARGET_ENV" >&2; exit 1; }
+  eval "$_env_exports"; unset _env_exports
 fi
 
 # Source EARLY (before any herdr usage in run_agent) — this is what turns