feat(p7-cli-namespace): rename colliding short flags to rsync parity (Wave A)

-c -> --checksum, -m -> --prune-empty-dirs, -M -> --remote-option,
-f -> --filter, -s -> --secluded-args, -p -> --perms, -T -> --temp-dir;
-a/--archive is now real rsync -rlptgoD (links+metadata+devices+specials).

FastSync's own flags moved to long-form-only or new shorts:
-j/--threads (multithreading), --preserve (metadata), --sendfile,
--chunk-serialization, --timeout, --ssh-port. Client-side only; the
wire config fields are unchanged (no PROTOCOL_VERSION bump). The server
keeps -p as its port. Docs (README, RSYNC_COMPAT summary 129->132) and
unit/integration tests updated. 37/37 unit, 400-pass integration.

tests/integration/test_tls.py

@@ -132,7 +132,7 @@ class TestTLSBasic:
             ])
             result, dur = run_client(
                 SOURCE_DIR, DEST_DIR,
-                flags=["-c", "--tls",
+                flags=["-z", "--tls",
                        "--cert", certs["client_cert"], "--key", certs["client_key"],
                        "--ca", certs["ca"]],
                 port=server.port,
@@ -157,7 +157,7 @@ class TestTLSBasic:
             ])
             result, dur = run_client(
                 SOURCE_DIR, DEST_DIR,
-                flags=["-m", "--tls",
+                flags=["--threads", "--tls",
                        "--cert", certs["client_cert"], "--key", certs["client_key"],
                        "--ca", certs["ca"]],
                 port=server.port,