fix(delete): match rsync deletion semantics (#290)

- Scope the --delete extras walk to directories synchronized by the
  transfer: add a synchronized-directory section to the delete manifest
  (protocol 2.23.0) so --files-from subsets no longer delete untransmitted
  paths outside listed directory subtrees (data-loss fix).
- Separate --max-size/--min-size prune protection from --delete-excluded so
  size-pruned source mirrors survive (rsync parity).
- Unlink extraneous destination symlinks instead of skipping them.
- Make --max-delete partial (delete up to N, skip the rest) and exit 25;
  accept negative values as unlimited.
- Draw --delete-missing-args deletions from the shared --max-delete budget.
- Honor --force during --delay-updates publication.

Add unit and integration regression tests; update the pinned config wire
golden and version strings for the 2.23.0 manifest/status additions.

src/server/receiver.h

@@ -4,6 +4,7 @@
 #include "config.h"
 #include "file.h"
 #include "file_receive.h"
+#include "protocol.h"
 #include <stdbool.h>
 #include <time.h>
 
@@ -21,6 +22,12 @@ typedef struct {
 
 typedef bool (*ReceiverSuccessFrame)(int fd, void* context);
 
+/* Records that a --max-delete commit stopped with extras left over, so the
+   caller's terminal success frame can carry STATUS_DELETE_LIMIT instead of
+   STATUS_OK.  The commit runs on the receiver thread, so the flag is stored in
+   the sink's own context rather than in a shared global. */
+typedef void (*ReceiverNoteDeleteLimit)(void* context);
+
 typedef struct {
   ReceiverFileSink store_file;
   void* context;
@@ -28,13 +35,18 @@ typedef struct {
   bool send_success;
   /* Emits the end-of-transfer success frame.  When the sender requested
      --remove-source-files this includes one per-file status per processed
-     data file followed by the final STATUS_OK; otherwise just STATUS_OK. */
+     data file followed by the final status; otherwise just the final status. */
   ReceiverSuccessFrame send_success_frame;
+  /* Optional; may be NULL when the sink has no --max-delete handling. */
+  ReceiverNoteDeleteLimit note_delete_limit;
 } ReceiverSink;
 
 bool receiver_outcomes_append(ReceiverOutcomes* outcomes, unsigned char code);
 void receiver_outcomes_destroy(ReceiverOutcomes* outcomes);
-bool receiver_send_final_success(int fd, const Config* config, const ReceiverOutcomes* outcomes);
+/* Send the terminal success frame.  `final_status` is usually STATUS_OK, or
+   STATUS_DELETE_LIMIT when a --max-delete commit was capped. */
+bool receiver_send_final_success(int fd, const Config* config, const ReceiverOutcomes* outcomes,
+                                 Status final_status);
 
 int receiver_process(Config* config, int file_descriptor, const ReceiverSink* sink);
 /* receiver_process with an escape hatch for the commit-style (late) deletion: