Send content expression component deps in SX responses for client routing

When a page has a content expression but no data dependency, compute its
transitive component deps and pass them as extra_component_names to
sx_response(). This ensures the client has all component definitions
needed for future client-side route rendering.

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

shared/sx/pages.py

@@ -279,13 +279,25 @@ async def execute_page(
     is_htmx = is_htmx_request()
 
     if is_htmx:
+        # Compute content expression deps so the server sends component
+        # definitions the client needs for future client-side routing
+        extra_deps: set[str] | None = None
+        if page_def.content_expr is not None and page_def.data_expr is None:
+            from .deps import components_needed
+            from .parser import serialize
+            try:
+                content_src = serialize(page_def.content_expr)
+                extra_deps = components_needed(content_src, get_component_env())
+            except Exception:
+                pass  # non-critical — client will just fall back to server
+
         return sx_response(await oob_page_sx(
             oobs=oob_headers if oob_headers else "",
             filter=filter_sx,
             aside=aside_sx,
             content=content_sx,
             menu=menu_sx,
-        ))
+        ), extra_component_names=extra_deps)
     else:
         return await full_page_sx(
             tctx,