fix(parity): receiver temp-dir confinement, server I/O floor, delete budget

Address review findings on feat/rsync-parity:
- confine --temp-dir below the receive root (reject absolute/.. like
  backup-dir/partial-dir); keep EXDEV non-atomic fallback
- floor server session I/O deadlines at SERVER_IO_TIMEOUT_SEC (60s) and
  install it on the socket layer at startup (slow-loris)
- charge each --delete-missing-args directory removal once and clamp the
  extras-walk remaining budget so it can never underflow past --max-delete
- normalize --compress-choice=auto to zstd client-side and accept it on
  receive so auto transfers no longer fail
- map received --max-alloc=0 to MAX_SERVER_ALLOC (receive path only)
- zero File.dest_state; include log-file-format in report_dest_info;
  add STATUS_DELETE_LIMIT name; recognize --skip-compress as a
  separate-value option; OOM-guard send_list_only root entry; drop the
  dead -M= branch; record the bare relative protected prefix for -R
  size-prunes in both scanners; refresh delete-manifest comment
- pin the rsync tarball sha256 and bump integrator image to v11

Tests: temp-dir rejection/relative/cross-device, server timeout floor,
delete-missing dir budget regression, compress-choice=auto e2e,
max-alloc=0 receive mapping, dest_state, report_dest_info modes,
skip-compress dash value, -M short forms, -R root size-prune mirror
protection (rsync 3.4.1 confirmed).

src/shared/config.h

@@ -328,9 +328,10 @@ typedef struct Config {
   char* tls_key;
   char* tls_ca;
   /* --timeout: per-message I/O deadline in seconds.  0 (rsync's default)
-   * disables the deadline entirely on both the socket layer and the protocol
-   * layer; a positive value sets it.  See protocol_session_set_io_timeout and
-   * tcp_set_timeouts. */
+   * disables the deadline entirely on the client's own socket and protocol
+   * layers; a positive value sets it.  A server session never inherits the
+   * disabled value: it applies the SERVER_IO_TIMEOUT_SEC floor (see
+   * protocol_server_io_timeout_sec and tcp_set_timeouts). */
   int timeout;
   /* --contimeout: connect()/accept timeout in seconds (rsync's default 60);
    * 0 disables it.  Transport layer only. */