feat: add structured per-file change output model (-i, --list-only, --out-format, --log-file-format)

Implement rsync-style itemized output backed by one shared change-event
engine (src/client/change_list.c):
- -i/--itemize-changes prints ">f+++++++++ <path>" for files actually sent
  (single-threaded and -m); unchanged files print nothing.
- --list-only prints an ls-style listing of files that would be transferred
  without contacting the server or writing anything.
- --out-format=FORMAT prints a printf-style template per changed file
  (tokens %%f %%n %%l %%b %%M %%%%; unknown escapes preserved).
- --log-file-format=FMT logs each transferred file when --log-file is set.
Events are emitted from the per-file sender path shared by both transfer
modes, so the single sender thread is the only reporter (no races).

src/client/client_cli.c

@@ -390,6 +390,10 @@ static const OptionEntry OPTION_TABLE[] = {
     {"--fsync", NULL, OPT_FLAG, offsetof(Config, use_fsync)},
     {"--checksum", NULL, OPT_FLAG, offsetof(Config, checksum)},
     {"--8-bit-output", "-8", OPT_FLAG, offsetof(Config, eight_bit_output)},
+    {"--itemize-changes", "-i", OPT_FLAG, offsetof(Config, itemize_changes)},
+    {"--list-only", NULL, OPT_FLAG, offsetof(Config, list_only)},
+    {"--out-format", NULL, OPT_STRING, offsetof(Config, out_format)},
+    {"--log-file-format", NULL, OPT_STRING, offsetof(Config, log_file_format)},
     {"--existing", NULL, OPT_FLAG, offsetof(Config, existing)},
     {"--ignore-existing", NULL, OPT_FLAG, offsetof(Config, ignore_existing)},
     {"--chmod", NULL, OPT_STRING, offsetof(Config, chmod_spec)},