Rewrite CLI around action runtime

tests/test_static_mutation_guard.py

@@ -0,0 +1,45 @@
+"""Static guard for direct filesystem mutation outside adapters/actions."""
+
+from __future__ import annotations
+
+import re
+from pathlib import Path
+
+
+MUTATING_PATTERNS = (
+    re.compile(r"\.(mkdir|unlink|write_text|write_bytes|symlink_to|chmod)\("),
+    re.compile(r"\b(os\.replace|shutil\.rmtree|shutil\.copy2|shutil\.copytree)\("),
+    re.compile(r"runtime\.fs\.(create_symlink|remove_symlink|write_json|write_text|write_bytes|copy_file|copy_tree|remove_file|remove_tree)\("),
+)
+
+ALLOWED_PREFIXES = (
+    Path("src/flow/adapters"),
+    Path("src/flow/actions"),
+    Path("tests"),
+)
+
+ALLOWED_FILES = {
+    Path("src/flow/core/paths.py"),
+}
+
+SKIPPED_LEGACY_COMMANDS = {
+    Path("src/flow/commands/completion.py"),
+}
+
+
+def test_no_direct_filesystem_mutation_outside_action_boundary():
+    root = Path(__file__).resolve().parents[1]
+    offenders: list[str] = []
+    for path in sorted((root / "src" / "flow").rglob("*.py")):
+        rel = path.relative_to(root)
+        if rel in ALLOWED_FILES or rel in SKIPPED_LEGACY_COMMANDS:
+            continue
+        if any(rel.is_relative_to(prefix) for prefix in ALLOWED_PREFIXES):
+            continue
+        for line_no, line in enumerate(path.read_text(encoding="utf-8").splitlines(), 1):
+            if "Service(" in line:
+                continue
+            if any(pattern.search(line) for pattern in MUTATING_PATTERNS):
+                offenders.append(f"{rel}:{line_no}: {line.strip()}")
+
+    assert offenders == []