Include layout + content component deps in streaming page scan

The streaming page's component scan only covered the suspense
placeholders, missing transitive deps from layout headers (e.g.
~cart-mini, ~auth-menu). Add layout.component_names to Layout class
and include them plus page content_expr in the scan source.

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

shared/sx/pages.py

@@ -426,9 +426,15 @@ async def execute_page_streaming(
         content=SxExpr(suspense_content_sx),
     )
 
-    # Pass the SX source for component scanning (resolution scripts may
-    # contain component calls that the client needs to render)
-    page_sx_for_scan = f'(~app-body :header-rows {suspense_header_sx} :content {suspense_content_sx})'
+    # Include layout component refs + page content so the scan picks up
+    # their transitive deps (e.g. ~cart-mini, ~auth-menu in headers).
+    layout_refs = ""
+    if layout is not None and hasattr(layout, "component_names"):
+        layout_refs = " ".join(f"({n})" for n in layout.component_names)
+    content_ref = ""
+    if page_def.content_expr is not None:
+        content_ref = sx_serialize(page_def.content_expr)
+    page_sx_for_scan = f'(<> {layout_refs} {content_ref} (~app-body :header-rows {suspense_header_sx} :content {suspense_content_sx}))'
     shell, tail = sx_page_streaming_parts(
         tctx, initial_page_html, page_sx=page_sx_for_scan,
     )