Fix /results polling: use sx_response() for SX wire format

The /results endpoint returns SX wire format but was sending it with
content-type text/html. The SX engine couldn't process it, so raw
s-expressions appeared as text and the browser tried to resolve
quoted strings like "a.jpg" as URLs.

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

test/bp/dashboard/routes.py

@@ -89,6 +89,7 @@ def register(url_prefix: str = "/") -> Blueprint:
     async def results():
         """HTMX partial — poll target for results table."""
         from shared.browser.app.csrf import generate_csrf_token
+        from shared.sx.helpers import sx_response
         from sxc.pages.renders import render_results_partial_sx
         import runner
 
@@ -104,10 +105,9 @@ def register(url_prefix: str = "/") -> Blueprint:
             active_service=active_service,
         )
 
-        resp = Response(html, status=200, content_type="text/html")
-        # If still running, tell HTMX to keep polling
+        headers = {}
         if running:
-            resp.headers["HX-Trigger-After-Swap"] = "test-still-running"
-        return resp
+            headers["HX-Trigger-After-Swap"] = "test-still-running"
+        return sx_response(html, headers=headers)
 
     return bp