docs(set_leds): note that segment start/length are now optional

The set_leds service handler is already pass-through, so the new
server-side defaults (start=0, length=rest-of-strip) work with no
code change. Refresh the field descriptions in services.yaml and
strings.json so the UI surfaces the simpler {"mode","color"} payload.

custom_components/ledgrab/strings.json

@@ -29,6 +29,9 @@
     "button": {
       "activate_scene": {
         "name": "{scene_name}"
+      },
+      "sync_clock_reset": {
+        "name": "Reset"
       }
     },
     "light": {
@@ -39,6 +42,9 @@
     "switch": {
       "processing": {
         "name": "Processing"
+      },
+      "sync_clock_running": {
+        "name": "Running"
       }
     },
     "sensor": {
@@ -56,6 +62,9 @@
       },
       "mapped_lights": {
         "name": "Mapped Lights"
+      },
+      "sync_clock_elapsed": {
+        "name": "Elapsed Time"
       }
     },
     "number": {
@@ -76,6 +85,9 @@
       },
       "api_input_timeout": {
         "name": "Fallback Timeout"
+      },
+      "sync_clock_speed": {
+        "name": "Speed"
       }
     },
     "select": {
@@ -106,7 +118,7 @@
         },
         "segments": {
           "name": "Segments",
-          "description": "List of segment objects with start, length, mode, and color/colors fields."
+          "description": "List of segment objects. start and length are optional (default to 0 and the rest of the strip); mode is one of solid/per_pixel/gradient with color or colors."
         }
       }
     }