Add loadable UI-format LTX audio workflow (API format didn't load in the canvas)

The canvas Load expects the UI graph format (nodes[]+links[]+positions), not the
API format — so the _api.json came up empty. Added workflow_ltx_audio.json in UI
format (matched the schema from a real workflow: node dicts with pos/size/inputs/
outputs/widgets_values, link tuples, version 0.4), validated slots/links. Dropped
audio_upload from AudioWaveSegments so the widget layout is predictable (the JS
upload button stays). README points to the loadable file; _api.json kept for the bridge.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

nodes/audio_wave_segments.py

@@ -92,7 +92,8 @@ class AudioWaveSegments:
     def INPUT_TYPES(cls):
         return {
             "required": {
-                "audio": (_audio_files(), {"audio_upload": True}),
+                # Pick a file from ComfyUI/input, or use the widget's "upload" button (JS).
+                "audio": (_audio_files(),),
                 "fps": ("INT", {"default": 24, "min": 1, "max": 120}),
                 "max_segments": ("INT", {"default": 6, "min": 3, "max": 12}),
                 "notes": ("STRING", {"default": "", "multiline": True}),