Detect fast→full mode change + auto-enable UI for ui-variant binary

Pipeline routing: when discovered files outnumber stored hashes by
>50%, the DB was built with a narrower file set (fast mode). Delete
and do a fresh parallel full index instead of single-threading
thousands of "new" files through the incremental path.

UI config: auto-enable ui_enabled when no config file exists and
the binary has embedded UI assets (CBM_EMBEDDED_FILE_COUNT > 0).
Previously the UI variant required --ui=true on first run.

Author: DeusData

src/pipeline/pipeline.c

@@ -382,12 +382,23 @@ int cbm_pipeline_run(cbm_pipeline_t *p) {
                     cbm_store_close(check_store);
 
                     if (hash_count > 0) {
-                        cbm_log_info("pipeline.route", "path", "incremental", "stored_hashes",
-                                     itoa_buf(hash_count));
-                        rc = cbm_pipeline_run_incremental(p, db_path, files, file_count);
-                        cbm_discover_free(files, file_count);
-                        free(db_path);
-                        return rc;
+                        /* Detect mode change (e.g. fast→full): if discovered files
+                         * outnumber stored hashes by >50%, the DB was built with a
+                         * narrower file set.  Delete and reindex fresh instead of
+                         * single-threading ~thousands of "new" files incrementally. */
+                        if (file_count > hash_count + (hash_count / 2)) {
+                            cbm_log_info("pipeline.route", "path", "mode_change_reindex",
+                                         "stored_hashes", itoa_buf(hash_count), "discovered",
+                                         itoa_buf(file_count));
+                            /* Falls through to delete-and-reindex below */
+                        } else {
+                            cbm_log_info("pipeline.route", "path", "incremental", "stored_hashes",
+                                         itoa_buf(hash_count));
+                            rc = cbm_pipeline_run_incremental(p, db_path, files, file_count);
+                            cbm_discover_free(files, file_count);
+                            free(db_path);
+                            return rc;
+                        }
                     }
                 } else if (check_store) {
                     cbm_store_close(check_store);

src/ui/config.c

@@ -5,6 +5,7 @@
  * Format: {"ui_enabled": false, "ui_port": 9749}
  */
 #include "ui/config.h"
+#include "ui/embedded_assets.h"
 #include "foundation/log.h"
 #include "foundation/platform.h"
 #include "foundation/compat_fs.h"
@@ -37,7 +38,11 @@ void cbm_ui_config_load(cbm_ui_config_t *cfg) {
 
     FILE *f = fopen(path, "rb");
     if (!f) {
-        return; /* no config file → defaults */
+        /* No config file — auto-enable UI if binary has embedded assets */
+        if (CBM_EMBEDDED_FILE_COUNT > 0) {
+            cfg->ui_enabled = true;
+        }
+        return;
     }
 
     fseek(f, 0, SEEK_END);