feat(delete): per-directory delete plans for --delete-during/--delete-delay (protocol 2.24.0)

Stream one delete plan per source directory from sender to receiver instead of
a single whole-tree keep-set manifest:

- --delete-during applies each directory's extras as its plan arrives, before
  that directory's data (rsync's generator-order deletion).
- --delete-delay snapshots each directory's extras while the plan arrives and
  commits the removals only after a fully-successful transfer, so files created
  after the scan survive (matching rsync's delete-delay, not delete-after).
- Type conflicts (a destination file blocking a source directory, or vice
  versa) are cleared immediately in both modes, so the nested write succeeds.

The plan carries the destination-relative directory, its kept child directory
names and its kept child file names; the first frame also carries the global
protected prefixes, size-skipped prefixes and --delete-missing-args paths.
--delete-before keeps the existing whole-tree early manifest; plain --delete and
--delete-after keep the end-of-transfer manifest commit.

Preserves the existing safety surface: protected/size-skipped prefixes and the
--delay-updates/basis skips are honored at any depth, deletion is scoped to the
synchronized directories (--files-from), MAX_SERVER_DELETE_COUNT and
--max-delete (partial + exit 25) are shared across plans, symlinks are never
followed, and paths are confined to the receive root.

tests/test_client_cli.c

@@ -317,7 +317,7 @@ static void test_parse_args_protocol_accept_current() {
   Config* cfg = valid_client_config();
   EXPECT_NOT_NULL(cfg);
   char* argv_equals[] = {"fastsync",   "--source-dir", "/src",
-                         "--dest-dir", "/dst",         "--protocol=2.23.0"};
+                         "--dest-dir", "/dst",         "--protocol=2.24.0"};
   int positional_args[2];
   int positional_count = 0;
   EXPECT_EQ_INT(parse_args(cfg, 6, argv_equals, positional_args, &positional_count), 0);
@@ -327,7 +327,7 @@ static void test_parse_args_protocol_accept_current() {
   cfg = valid_client_config();
   EXPECT_NOT_NULL(cfg);
   char* argv_space[] = {"fastsync", "--source-dir", "/src",  "--dest-dir",
-                        "/dst",     "--protocol",   "2.23.0"};
+                        "/dst",     "--protocol",   "2.24.0"};
   positional_count = 0;
   EXPECT_EQ_INT(parse_args(cfg, 7, argv_space, positional_args, &positional_count), 0);
   EXPECT_EQ_STR(cfg->version, PROTOCOL_VERSION);