feat: define P2 host workspace command contract

tools/thothctl/internal/safeio/files_test.go

@@ -41,3 +41,37 @@ func TestReadCanonicalRegularRejectsFinalAndParentSymlinks(t *testing.T) {
 		t.Fatalf("final symlink error = %v, want ErrUnsafeFile", err)
 	}
 }
+
+func TestReadCanonicalUTF8RejectsNonUTF8AndBounds(t *testing.T) {
+	path := filepath.Join(t.TempDir(), "input.sql")
+	if err := os.WriteFile(path, []byte("\xff"), 0o600); err != nil {
+		t.Fatal(err)
+	}
+	if _, err := ReadCanonicalUTF8(path, 1024); !errors.Is(err, ErrUnsafeFile) {
+		t.Fatalf("ReadCanonicalUTF8 invalid UTF-8 = %v", err)
+	}
+	if err := os.WriteFile(path, []byte("12345"), 0o600); err != nil {
+		t.Fatal(err)
+	}
+	if _, err := ReadCanonicalUTF8(path, 4); !errors.Is(err, ErrUnsafeFile) {
+		t.Fatalf("ReadCanonicalUTF8 oversized = %v", err)
+	}
+}
+
+func TestWriteCanonicalExclusiveRejectsExistingAndCreatesPrivateFile(t *testing.T) {
+	root, err := filepath.EvalSymlinks(t.TempDir())
+	if err != nil {
+		t.Fatal(err)
+	}
+	path := filepath.Join(root, "candidate.yaml")
+	if err := WriteCanonicalExclusive(path, []byte("ok"), 0o600); err != nil {
+		t.Fatal(err)
+	}
+	contents, err := os.ReadFile(path)
+	if err != nil || string(contents) != "ok" {
+		t.Fatalf("output = %q, %v", contents, err)
+	}
+	if err := WriteCanonicalExclusive(path, []byte("replace"), 0o600); !errors.Is(err, ErrUnsafeFile) {
+		t.Fatalf("replacement = %v", err)
+	}
+}