feat: Versionsstelle als Kompatibilitaetsfrage, Breaking-Change-Vermerk erzwungen (2.5.0)

Files changed:
- CHANGES.md
- INSTALL.md
- VERSION
- instructions/dev/stack-dev/SKILL.md
- instructions/dev/version-parts.md
- tools/CONTRACT.md
- tools/chemenu/commands/docs_verify.py
- tools/chemenu/commands/version_cmd.py
- tools/chemenu/tests/test_docs_verify.py
- tools/chemenu/tests/test_version_cmd.py
- tools/chemenu/version.py

tools/chemenu/tests/test_docs_verify.py

@@ -237,6 +237,43 @@ def test_a_migration_document_satisfies_the_check(tmp_path, monkeypatch):
     assert docs_verify.check_migration_for_boundary() == []
 
 
+def test_a_breaking_release_without_a_breaking_note_is_reported(tmp_path, monkeypatch):
+    """A crossing that migrates nothing still leaves hand-work behind, so the
+    migration check passing is not evidence that anyone was told."""
+    from chemenu import version as version_mod
+
+    _boundary_tree(
+        tmp_path, monkeypatch, "2.0.0", "1.4.0",
+        marker=f"{version_mod.MIGRATION_NONE_MARKER} - nothing to change.\n\n",
+    )
+    assert docs_verify.check_migration_for_boundary() == []
+    issues = docs_verify.check_breaking_change_for_boundary()
+    assert any("2.0.0" in issue and "drop-in" in issue for issue in issues)
+
+
+def test_a_compatible_release_needs_no_breaking_note(tmp_path, monkeypatch):
+    _boundary_tree(tmp_path, monkeypatch, "1.5.0", "1.4.0")
+    assert docs_verify.check_breaking_change_for_boundary() == []
+
+
+def test_a_breaking_change_marker_satisfies_the_check(tmp_path, monkeypatch):
+    from chemenu import version as version_mod
+
+    _boundary_tree(
+        tmp_path, monkeypatch, "2.0.0", "1.4.0",
+        marker=f"{version_mod.BREAKING_CHANGE_MARKER} the feed moved.\n\n",
+    )
+    assert docs_verify.check_breaking_change_for_boundary() == []
+
+
+def test_verify_raises_when_a_boundary_has_no_breaking_note(monkeypatch):
+    monkeypatch.setattr(
+        docs_verify, "check_breaking_change_for_boundary", lambda: ["unannounced"]
+    )
+    with pytest.raises(typer.Exit):
+        docs_verify.verify()
+
+
 def test_verify_raises_when_a_boundary_has_no_migration(monkeypatch):
     monkeypatch.setattr(docs_verify, "check_migration_for_boundary", lambda: ["unbridged"])
     with pytest.raises(typer.Exit):