fix(issue-26): review round 1 - no file key assigns bash's own variables; SKS_QUIESCENT_TRIES; long decimals

R1 (P1): a quoted export still ran code when the key was a bash special
variable (RANDOM=a[$(cmd)] is evaluated arithmetically on assignment).
envfile.RESERVED (bash's own variables, plus BASH_/COMP_/READLINE_
prefixes) is skipped with a line-numbered warning by both loaders; a test
keeps it covering every variable a clean bash defines. The wrapper also
hands SCRIPT_DIR/REPO_ROOT/TARGET_ENV to the parser as environment, so the
file cannot replace the variables it has already set.

R2 (P2): SKS_QUIESCENT_TRIES reached `for ((i < tries))` through a function
argument; it is normalised at the call site (minimum 0). B5 now requires
every integer-looking env default in the shell code to be normalised or
listed in NOT_ARITHMETIC with where it goes, and exercises _pane_quiescent.

R3 (P2): _positive_int strips leading zeros and rejects more than nine
significant digits before int(), like mam_int; 5000-digit inputs no longer
raise in the runner.

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

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

@@ -35,9 +35,12 @@ if [[ -z "$TARGET_ENV" ]]; then
 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.
+# never sourced. Values come back as shlex-quoted exports over the pipe. The
+# variables this script has already set are handed over as environment, so
+# the file cannot replace them either.
 if [[ -n "$TARGET_ENV" && -f "$TARGET_ENV" ]]; then
-  _env_exports="$("${DELEGATE_JOB_PYTHON:-python3}" -I "$SCRIPT_DIR/../lib_py/delegation/envfile.py" --shell "$TARGET_ENV")" \
+  _env_exports="$(SCRIPT_DIR="$SCRIPT_DIR" REPO_ROOT="$REPO_ROOT" TARGET_ENV="$TARGET_ENV" \
+    "${DELEGATE_JOB_PYTHON:-python3}" -I "$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