refactor(client): split reporting/scan/manifest out of client_send

Move the stats/progress reporting, scanner-preparation/scan helpers and
manifest/list/dry-run senders out of the ~3.9k-line client_send.c into
client_report.c, client_scan.c and client_manifest.c, sharing declarations
through the new internal client_send_internal.h.  client_send.c keeps the
transfer orchestration and is now ~2.1k lines.

Decompose the monolithic send_files into static phase helpers
(send_files_prepare/_prepare_delete/_run/_finalize/_cleanup) driven by a
single SendFilesState; ownership, ordering and exit codes are unchanged.

No behavior change.

src/client/client_send_internal.h

@@ -0,0 +1,91 @@
+#ifndef CLIENT_SEND_INTERNAL_H
+#define CLIENT_SEND_INTERNAL_H
+
+/* Declarations shared between the client_send.c transfer orchestration and the
+ * reporting (client_report.c), scanner-preparation (client_scan.c) and
+ * manifest/list/dry-run (client_manifest.c) translation units that were split
+ * out of it.  Nothing here is part of the public client_send.h facade. */
+
+#include "array_list.h"
+#include "client_send.h"
+#include "config.h"
+#include "delete_plan.h"
+#include "delta.h"
+#include "format.h"
+#include "log.h"
+#include "scanner.h"
+#include <stdatomic.h>
+#include <stdbool.h>
+#include <stddef.h>
+#include <time.h>
+
+/* One mebibyte in bytes; the unit used by the --stats/--progress lines.
+   Always cast to double when dividing so the output stays fractional. */
+#define BYTES_PER_MIB (1024ULL * 1024ULL)
+
+/* Compiled scanner inputs that are shared read-only across scanner instances
+ * and, in -m mode, across worker threads. `base_filters` owns the compiled
+ * command-line + -C rules; the FileListSet allow-set lives in the Config.
+ * `hardlinks` owns the --hard-links/-H link-group detection table (NULL when
+ * off) and is shared (mutex-guarded) across every scanner/worker of one scan. */
+typedef struct {
+  ScannerOptions options;
+  FilterRuleList* base_filters; /* owned; may be NULL */
+  HardLinkTable* hardlinks;     /* owned; may be NULL */
+  char* relative_prefix;        /* owned -R prefix; may be NULL */
+} PreparedScanner;
+
+/* client_scan.c */
+bool prepare_scanner(const Config* config, int num_threads, PreparedScanner* out);
+void prepared_scanner_destroy(PreparedScanner* prepared);
+bool append_implied_dir_times(const Config* config, ArrayList* dir_entries);
+char* delete_scope_root_marker(const Config* config);
+const char* delete_plan_walk_root(const Config* config, const ArrayList* synced_dirs);
+bool files_from_list_check(const Config* config, ArrayList* missing_dest, int* skipped_out);
+bool scan_paths_only(const Config* config, const ScannerOptions* options, ArrayList* manifest,
+                     DeletePlanSender* plans, bool* io_error_out,
+                     unsigned long long* non_dir_count_out);
+
+/* client_report.c */
+void log_server_rejection(const char* context);
+const char* display_bytes(unsigned long long bytes, bool human_readable, char* buffer,
+                          size_t buffer_size);
+unsigned long long dir_count_for_stats(const Config* config, const ArrayList* dir_entries,
+                                       atomic_ullong* counter);
+void report_transfer_stats(const Config* config, const TransferStats* stats, time_t start,
+                           const ReceiverStats* recv);
+void transfer_stats_note_entry(TransferStats* stats, const File* file);
+void transfer_stats_note_transferred(TransferStats* stats, const File* file);
+bool info_flag_enabled(const Config* config, LogInfoFlag flag);
+void print_delete_reports(const Config* config, const ArrayList* paths);
+const char* delete_display_path(const Config* config, const char* path);
+bool progress_requested(const Config* config);
+void client_progress_cleanup(void);
+void client_progress_begin(const Config* config);
+void client_progress_file(const Config* config, const File* file);
+void client_progress_name(const Config* config, const File* file);
+void client_progress_uptodate(const Config* config, const File* file);
+void client_progress_prepare(const Config* config, const ArrayList* plan_dirs,
+                             unsigned long long plan_non_dir_count);
+bool receive_stats_record(int fd, ReceiverStats* stats, ArrayList* would_delete);
+
+/* client_send.c */
+void receive_daemon_motd(Client* client, const Config* config);
+Client* connect_transfer_client(const Config* config);
+void disconnect_transfer_client(Client* client);
+int incremental_check(Client* client, File* file, const Config* config, DeltaSignature** out_sig,
+                      unsigned long long* resume_offset);
+
+/* client_manifest.c */
+bool dry_run_targets_server(const Config* config);
+bool add_chunk_to_manifest(ArrayList* manifest, const Chunk* chunk);
+int send_dry_run_manifest(const Config* config);
+int send_list_only(const Config* config);
+int send_dry_run_remote(Config* config);
+int send_delete_manifest(int fd, ArrayList* manifest, ArrayList* protected_prefixes,
+                         ArrayList* size_skipped, ArrayList* missing_args, ArrayList* synced_dirs);
+bool send_delete_manifest_early(Client* client, ArrayList* manifest, ArrayList* protected_prefixes,
+                                ArrayList* size_skipped, ArrayList* missing_args,
+                                ArrayList* synced_dirs);
+
+#endif