feat(app): bootstrap gradio blocks with brutalist mono chrome

app.py

@@ -0,0 +1,73 @@
+"""ACE Music Studio — Gradio entrypoint.
+
+On HF Spaces, `_bootstrap()` runs once on import to mirror the read-only
+preload cache into a writable tree. On Mac/Linux locally, it's a no-op.
+The backend singleton is lazy-loaded on first generation request.
+"""
+from __future__ import annotations
+
+import os
+
+# Set MPS fallback BEFORE any torch import path is taken.
+os.environ.setdefault("PYTORCH_ENABLE_MPS_FALLBACK", "1")
+
+# Don't pin HF download source — let HF default for both Spaces and local cache.
+os.environ.setdefault("HF_HUB_ENABLE_HF_TRANSFER", "1")
+
+import gradio as gr
+
+import theme
+
+HEADER_HTML = """
+<div class="ams-header">
+  <div>
+    <div class="ams-brand">ACE Music Studio<span class="ams-brand-period">.</span></div>
+  </div>
+  <div class="ams-status">ready</div>
+</div>
+""".strip()
+
+CTA_HTML = """
+<div class="ams-cta">
+  Built with <span class="ams-cta-heart">♥</span>.
+  <strong>Drop a like</strong> at the top
+  &nbsp;·&nbsp;
+  Follow <a href="https://huggingface.co/techfreakworm" target="_blank" rel="noopener noreferrer"><strong>@techfreakworm</strong></a>
+  for what's next.
+</div>
+""".strip()
+
+
+def _bootstrap() -> None:
+    """HF Spaces: mirror read-only preload cache into a writable tree.
+
+    Local Mac/CUDA: no-op. Implemented at M7 when we wire deployment.
+    """
+    pass
+
+
+def build_app() -> gr.Blocks:
+    with gr.Blocks(theme=theme.build_theme(), css=theme.CSS, title="ACE Music Studio") as demo:
+        gr.HTML(HEADER_HTML)
+        gr.HTML(CTA_HTML)
+
+        with gr.Tabs():
+            with gr.Tab("🎵 Generate"):
+                gr.Markdown("Generate tab placeholder — implemented in M1.")
+            with gr.Tab("🎤 Cover"):
+                gr.Markdown("Cover tab placeholder — implemented in M3.")
+            with gr.Tab("⏩ Extend"):
+                gr.Markdown("Extend tab placeholder — implemented in M3.")
+            with gr.Tab("✏️ Edit"):
+                gr.Markdown("Edit tab placeholder — implemented in M3.")
+            with gr.Tab("✍️ Lyrics"):
+                gr.Markdown("Lyrics tab placeholder — implemented in M4.")
+
+    return demo
+
+
+if __name__ == "__main__":
+    _bootstrap()
+    demo = build_app()
+    demo.queue(default_concurrency_limit=1)
+    demo.launch(server_name="0.0.0.0", server_port=int(os.environ.get("PORT", 7860)))