Restore stashed WIP: live streaming plan, forms, CI pipeline, streaming demo

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

sx/sxc/pages/helpers.py

@@ -838,19 +838,40 @@ def _data_test_data() -> dict:
     }
 
 
-async def _streaming_demo_data() -> dict:
-    """Simulate slow IO for streaming demo — 1.5s delay."""
+async def _streaming_demo_data():
+    """Multi-stream demo — yields three chunks at staggered intervals.
+
+    Each yield is a dict with _stream_id (matching a ~suspense :id in the
+    shell) plus bindings for the :content expression. The streaming
+    infrastructure detects the async generator and resolves each suspense
+    placeholder as each chunk arrives.
+    """
     import asyncio
-    await asyncio.sleep(1.5)
     from datetime import datetime, timezone
-    return {
-        "streamed-at": datetime.now(timezone.utc).isoformat(timespec="seconds"),
-        "message": "This content was streamed after a 1.5 second delay.",
-        "items": [
-            {"label": "Shell", "detail": "HTML shell with suspense placeholders sent immediately"},
-            {"label": "Bootstrap", "detail": "sx-browser.js loads, renders fallback skeletons"},
-            {"label": "IO Start", "detail": "Data fetch and header fetch run concurrently"},
-            {"label": "Resolve", "detail": "As each IO completes, <script> chunk replaces placeholder"},
-            {"label": "Done", "detail": "Page fully rendered — all suspense resolved"},
-        ],
+
+    await asyncio.sleep(1)
+    yield {
+        "stream-id": "stream-fast",
+        "stream-label": "Fast API",
+        "stream-color": "green",
+        "stream-message": "Responded in ~1 second",
+        "stream-time": datetime.now(timezone.utc).isoformat(timespec="seconds"),
+    }
+
+    await asyncio.sleep(2)  # 3s total
+    yield {
+        "stream-id": "stream-medium",
+        "stream-label": "Database Query",
+        "stream-color": "blue",
+        "stream-message": "Query completed in ~3 seconds",
+        "stream-time": datetime.now(timezone.utc).isoformat(timespec="seconds"),
+    }
+
+    await asyncio.sleep(2)  # 5s total
+    yield {
+        "stream-id": "stream-slow",
+        "stream-label": "ML Inference",
+        "stream-color": "amber",
+        "stream-message": "Model inference completed in ~5 seconds",
+        "stream-time": datetime.now(timezone.utc).isoformat(timespec="seconds"),
     }