fix(issue-42): review R1 - stop's exit 1 also comes after the stop

The registry update after the kill chain raises SystemExit(1) when the row
disappeared during the run (stop_session.sh:310), so "exit 1 changed nothing"
was false on that path. The stop table now says so, the code is declared as a
passthrough, and the test requires every integer SystemExit in an entry
script's heredocs to be declared - the check that would have caught it.

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

tests/data/skill_code_blocks.json

@@ -593,7 +593,9 @@
     "4",
     "other"
    ],
-   "passthrough": {}
+   "passthrough": {
+    "1": "multi-agent-mux-stop/scripts/stop_session.sh:310"
+   }
   },
   "multi-agent-mux-create/scripts/create_session.sh": {
    "skill": "multi-agent-mux-create",
@@ -616,6 +618,7 @@
   "C4: create named a nonexistent `agent-sessions-yaml-edit` script; removed (create_session.sh writes the row)",
   "C5: create's cmd_full table (claude = `claude`) disagreed with adapter spawn-spec; replaced by \"decided by spawn-spec\"",
   "C6: create_session.sh header lists exit 4 \"YAML append failure\"; there is no literal `exit 4`, but the YAML write raises SystemExit(4) for a duplicate running row (create_session.sh:515) and it passes through, so 4 IS a real exit code (the plan assumed it was not)",
-  "R6: resume's \"The script above re-passes them\" and \"as done in Workflow above\" pointed at the removed block; reworded (same for create's Verification note)"
+  "R6: resume's \"The script above re-passes them\" and \"as done in Workflow above\" pointed at the removed block; reworded (same for create's Verification note)",
+  "R7 (review 08e1f1b2): stop's table said exit 1 is always pre-stop; the registry update after the kill chain also raises SystemExit(1) (stop_session.sh:310) when the row disappeared"
  ]
 }

tests/test_issue42_skill_blocks.py

@@ -54,22 +54,34 @@ _HEREDOC = re.compile(r"(?<!<)<<-?\s*(['\"]?)(\w+)\1")
 _EXIT = re.compile(r"(?<![\w.])exit\s+(\d+)\b")
 
 
-def literal_exit_codes(script):
-    """Codes the entry script exits with literally: `exit N` in shell context.
+_RAISE = re.compile(r"SystemExit\((\d+)\)")
 
-    Only the entry file itself (not lib.sh or sub-scripts); heredoc bodies and
-    comment lines are skipped, and `sys.exit(N)` never matches."""
-    codes, pending = set(), []
-    for line in (SKILLS / script).read_text(encoding="utf-8").split("\n"):
+
+def _scan_exits(script):
+    """(`exit N` codes in shell context, {code: line} of `SystemExit(N)` in heredoc bodies).
+
+    Only the entry file itself (not lib.sh or sub-scripts). Comment lines are
+    skipped, and `sys.exit(N)` never matches `exit N`. A heredoc's SystemExit is
+    the exit code of the unguarded Python step under set -e."""
+    codes, raised, pending = set(), {}, []
+    for n, line in enumerate((SKILLS / script).read_text(encoding="utf-8").split("\n"), 1):
         if pending:
             if line.strip() == pending[0]:
                 pending.pop(0)
+            else:
+                for code in _RAISE.findall(line):
+                    raised.setdefault(code, n)
             continue
         if re.match(r"^\s*#", line):
             continue
         codes.update(_EXIT.findall(line))
         pending.extend(m.group(2) for m in _HEREDOC.finditer(line))
-    return codes
+    return codes, raised
+
+
+def literal_exit_codes(script):
+    """Codes the entry script exits with literally: `exit N` in shell context."""
+    return _scan_exits(script)[0]
 
 
 def exit_table(skill):
@@ -137,6 +149,9 @@ def test_exit_table_agrees_with_script(script):
     literal = literal_exit_codes(script)
     assert literal <= numeric, f"{script} exits with {sorted(literal - numeric)} but the table lacks them"
     passthrough = ep["passthrough"]
+    raised = _scan_exits(script)[1]
+    assert {c: f"{script}:{n}" for c, n in raised.items()} == passthrough, \
+        f"{script}: SystemExit codes in heredocs {raised} must be declared as passthrough (and in the table)"
     assert numeric <= literal | set(passthrough), \
         f"table codes {sorted(numeric - literal - set(passthrough))} come from nowhere in {script}"
     for code, ref in passthrough.items():