Add s-expression wire format support and test detail view

- HTMX beforeSwap hook intercepts text/sexp responses and renders
  them client-side via sexp.js before HTMX swaps the result in
- sexp_response() helper for returning text/sexp from route handlers
- Test detail page (/test/<nodeid>) with clickable test names
- HTMX navigation to detail returns sexp wire format (4x smaller
  than pre-rendered HTML), full page loads render server-side
- ~test-detail component with back link, outcome badge, and
  error traceback display

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

shared/sexp/helpers.py

@@ -9,6 +9,7 @@ from __future__ import annotations
 from typing import Any
 
 from markupsafe import escape
+from quart import Response
 
 from .jinja_bridge import render
 from .page import SEARCH_HEADERS_MOBILE, SEARCH_HEADERS_DESKTOP
@@ -225,6 +226,24 @@ def full_page(ctx: dict, *, header_rows_html: str,
     )
 
 
+def sexp_response(sexp_source: str, status: int = 200,
+                   headers: dict | None = None) -> Response:
+    """Return an s-expression wire-format response.
+
+    The client-side sexp.js will intercept responses with Content-Type
+    text/sexp and render them before HTMX swaps the result in.
+
+    Usage in a route handler::
+
+        return sexp_response('(~test-row :nodeid "test_foo" :outcome "passed")')
+    """
+    resp = Response(sexp_source, status=status, content_type="text/sexp")
+    if headers:
+        for k, v in headers.items():
+            resp.headers[k] = v
+    return resp
+
+
 def oob_page(ctx: dict, *, oobs_html: str = "",
              filter_html: str = "", aside_html: str = "",
              content_html: str = "", menu_html: str = "") -> str: