stack-dev/stack-close skill split; publish stack-machinery note; model-selection fix (#47 Block 2)

Files changed:
- CHANGES.md
- VERSION
- instructions/claude-code-model-selection.md
- instructions/dev/stack-close/SKILL.md
- instructions/dev/stack-dev/SKILL.md
- tools/CONTRACT.md
- tools/chemenu/commands/git_publish.py
- tools/chemenu/tests/test_git_publish.py

tools/chemenu/commands/git_publish.py

@@ -423,6 +423,41 @@ def counted_files_of(
     return [change for change in changes if not is_exempt(change.path, prefixes)]
 
 
+# The same scope `version-parts.md` names for the stack version itself -
+# "tools/, types/, instructions/, AGENTS.md and the contracts" - reused here
+# to decide whether a publish's changeset falls under it. Not a copy of that
+# rule: version-parts.md states the scope in prose for a human choosing a
+# version part, this instantiates the same boundary in code for a different
+# question (does this publish deserve the closing-phase reminder below).
+STACK_MACHINERY_PREFIXES = ("tools/", "types/", "instructions/")
+STACK_MACHINERY_NAMES = ("AGENTS.md",)
+
+STACK_MACHINERY_NOTE = (
+    "Note: this publish touched stack machinery. What a stack-dev session "
+    "does next - closing prose, a changelog entry's accuracy, whether a "
+    "docs/ page went stale - is not covered by docs verify, instructions "
+    "verify, or pytest. No tool checks it; a session has to."
+)
+
+
+def touches_stack_machinery(changed_files: list[str]) -> bool:
+    """Whether `changed_files` includes a path under `version-parts.md`'s
+    scope for the stack version - `tools/`, `types/`, `instructions/`,
+    `AGENTS.md`, or any `<stage>/CONTRACT.md`. A publish in this class is,
+    by construction of the `stack-dev`/`stack-close` split, always followed
+    by the unchecked closing phase - `STACK_MACHINERY_NOTE` times a reminder
+    to land exactly there, for any session, not only one that read the
+    skill that names it."""
+    for path in changed_files:
+        if path in STACK_MACHINERY_NAMES:
+            return True
+        if path.endswith("CONTRACT.md"):
+            return True
+        if path.startswith(STACK_MACHINERY_PREFIXES):
+            return True
+    return False
+
+
 YES_REMOVED_MESSAGE = (
     "--yes no longer exists. The Mass-Update Gate is cleared with `--confirm <token>`, and the "
     "token comes from the gate's own refusal output - run this command without it first to see "
@@ -1138,3 +1173,5 @@ def publish_command(
         },
     )
     success(f"Published changes to {remote}/{branch}." if push else "Committed changes (not pushed).")
+    if touches_stack_machinery(changed_files):
+        typer.echo(STACK_MACHINERY_NOTE)

tools/chemenu/tests/test_git_publish.py

@@ -10,6 +10,7 @@ from chemenu.commands._util import EXIT_NEEDS_CLEARANCE
 from chemenu.commands.git_publish import (
     DEFAULT_MASS_UPDATE_THRESHOLD,
     GATE_EXEMPT_PREFIXES,
+    STACK_MACHINERY_NOTE,
     YES_REMOVED_MESSAGE,
     FileChange,
     attention_notes,
@@ -29,6 +30,7 @@ from chemenu.commands.git_publish import (
     rerun_command,
     scale_line,
     sync_command,
+    touches_stack_machinery,
 )
 
 
@@ -290,6 +292,26 @@ def test_gate_message_names_generated_files_as_their_own_reason():
     assert "kb/provenance.md" not in message
 
 
+def test_stack_machinery_detects_the_version_parts_scope():
+    """The same boundary version-parts.md names for the stack version: tools/,
+    types/, instructions/, AGENTS.md, and any <stage>/CONTRACT.md."""
+    assert touches_stack_machinery(["instructions/dev/issue-tracking.md"])
+    assert touches_stack_machinery(["tools/chemenu/commands/git_publish.py"])
+    assert touches_stack_machinery(["types/instruction.md"])
+    assert touches_stack_machinery(["AGENTS.md"])
+    assert touches_stack_machinery(["kb/CONTRACT.md"])
+    assert touches_stack_machinery(["raw/CONTRACT.md"])
+
+
+def test_stack_machinery_excludes_ordinary_content():
+    """kb/ content, docs/ prose and work/ scratch carry no normative sentence
+    and are not what the closing-phase reminder is about."""
+    assert not touches_stack_machinery(["kb/entities/systems/Foo.md"])
+    assert not touches_stack_machinery(["docs/why-gates-are-code.md"])
+    assert not touches_stack_machinery(["work/ingest-x/extract-0.md"])
+    assert not touches_stack_machinery([])
+
+
 # --- publish_command integration: a real git repo + a local bare remote ---
 
 
@@ -356,6 +378,24 @@ def test_below_threshold_publish_goes_straight_through(repo):
     assert _git(repo, "status", "--porcelain", "-uall").stdout == ""
 
 
+def test_publish_notes_stack_machinery_after_success(repo, capsys):
+    """The closing-phase reminder lands exactly once, after the OK line, and
+    only when the changeset actually falls under version-parts.md's scope."""
+    (repo / "instructions").mkdir()
+    (repo / "instructions/example.md").write_text("x\n", encoding="utf-8")
+    _publish(message="touch instructions")
+    out = capsys.readouterr().out
+    assert STACK_MACHINERY_NOTE in out
+    assert out.count(STACK_MACHINERY_NOTE) == 1
+
+
+def test_publish_stays_quiet_for_ordinary_content(repo, capsys):
+    _write_files(repo, 1)
+    _publish(message="ordinary content")
+    out = capsys.readouterr().out
+    assert STACK_MACHINERY_NOTE not in out
+
+
 def test_at_threshold_publish_asks_for_clearance_and_stages_nothing(repo):
     _write_files(repo, 10)
     with pytest.raises(typer.Exit) as excinfo: