devices: --devices/--specials/-D/--copy-devices/--write-devices

Recreate char/block nodes via mknodat (privilege-gated, EPERM->warn+skip) and
FIFOs via mkfifoat; new STATUS_SPECIAL frame + validated rdev; sockets skipped;
-copy-devices copies st_size; -write-devices O_NOFOLLOW+O_NONBLOCK warn+skip.
preserve_specials/copy_devices/write_devices cross the wire. PROTOCOL_VERSION
2.12.0->2.13.0. Review fixes: -m source-removal keeps recreated specials, FIFO
ENXIO skip, rdev bounds at chunk_deserialize, STATUS_ERROR on receive branch,
scanner_prepare_special dedup.

tests/test_file.c

@@ -25,6 +25,26 @@ static void test_file_create() {
   file_destroy(f);
 }
 
+/* rdev/type validation shared by the wire path and the secure recreation site:
+ * a legal char/block major/minor pair is accepted, out-of-range / negative
+ * values and non-device entries carrying an rdev are rejected. */
+static void test_file_special_rdev_valid() {
+  mode_t fake_char = S_IFCHR | 0600;
+  mode_t fake_blk = S_IFBLK | 0600;
+  mode_t fake_fifo = S_IFIFO | 0600;
+  /* char/block devices: accept a legal pair, reject negative / oversized. */
+  EXPECT_TRUE(file_special_rdev_valid(1, 3, fake_char));
+  EXPECT_TRUE(file_special_rdev_valid(0xffff, 0x00ffffff, fake_blk));
+  EXPECT_FALSE(file_special_rdev_valid(-1, 3, fake_char));
+  EXPECT_FALSE(file_special_rdev_valid(1, -1, fake_char));
+  EXPECT_FALSE(file_special_rdev_valid(0x10000, 3, fake_char));
+  EXPECT_FALSE(file_special_rdev_valid(1, 0x1000000, fake_char));
+  /* FIFOs/sockets must carry an empty rdev. */
+  EXPECT_TRUE(file_special_rdev_valid(0, 0, fake_fifo));
+  EXPECT_FALSE(file_special_rdev_valid(1, 0, fake_fifo));
+  EXPECT_FALSE(file_special_rdev_valid(0, 0, (mode_t)(S_IFREG | 0600)));
+}
+
 static void test_file_destroy_null() {
   file_destroy(NULL);
 }
@@ -960,6 +980,7 @@ static void test_dir_entry_save_to_disk() {
 
 void test_file() {
   test_file_create();
+  test_file_special_rdev_valid();
   test_file_destroy_null();
   test_file_destroy_normal();
   test_file_load_data();