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>

test/sexp/sexp_components.py

@@ -208,3 +208,46 @@ async def render_results_partial(result: dict | None, running: bool,
     """HTMX partial: just the results section (wrapped in polling div)."""
     inner = _results_partial_html(result, running, csrf, active_filter, active_service)
     return _wrap_results_div(inner, running)
+
+
+async def render_test_detail_page(ctx: dict, test: dict) -> str:
+    """Full page: test detail view."""
+    hdr = _header_stack_html(ctx)
+    detail_row = render(
+        "menu-row",
+        id="test-detail-row", level=2, colour="sky",
+        link_href=f"/test/{test['nodeid']}",
+        link_label=test["nodeid"].rsplit("::", 1)[-1],
+    )
+    hdr += render("header-child", id="test-header-child",
+                  inner_html=detail_row)
+    content = render(
+        "test-detail",
+        nodeid=test["nodeid"],
+        outcome=test["outcome"],
+        duration=str(test["duration"]),
+        longrepr=test.get("longrepr", ""),
+    )
+    body_end = client_components_tag()
+    return full_page(ctx, header_rows_html=hdr, content_html=content,
+                     body_end_html=body_end)
+
+
+def test_detail_sexp(test: dict) -> str:
+    """Return s-expression wire format for a test detail view.
+
+    When a client has sexp.js loaded (HTMX navigation from the dashboard),
+    we can send the raw s-expression instead of pre-rendered HTML.
+    sexp.js will render it client-side.
+    """
+    from shared.sexp.parser import serialize
+    nodeid = serialize(test["nodeid"])
+    outcome = serialize(test["outcome"])
+    duration = serialize(str(test["duration"]))
+    longrepr = serialize(test.get("longrepr", ""))
+    return (
+        f"(section :id \"main-panel\""
+        f" :class \"flex-1 md:h-full md:min-h-0 overflow-y-auto overscroll-contain js-grid-viewport\""
+        f" (~test-detail :nodeid {nodeid} :outcome {outcome}"
+        f" :duration {duration} :longrepr {longrepr}))"
+    )