fix(runner/pinot): query the broker /query/sql path with controller fallback

[mayankpande88]

pinot_query always POSTed to /sql, but the chart directs operators to
point PINOT_URL at the Pinot broker, whose query path is /query/sql —
so every query 404'd on a broker-targeted PINOT_URL.

POST to /query/sql first (the documented broker setup) and fall back to
/sql on a 404, so both broker and controller URLs work. The /tables and
/schemas endpoints stay controller-only, as documented.

Co-Authored-By: Claude Opus 4.8 (1M context) noreply@anthropic.com
Claude-Session: https://claude.ai/code/session_01L2HAXQH1gEtX7h4sUJsi9j

[gemini-code-assist]

Code Review

This pull request updates the Pinot client to query the broker path (/query/sql) first and fall back to the controller path (/sql) upon receiving a 404 status code, allowing it to work with both broker and controller URLs. A new doRaw helper is introduced to return raw HTTP responses and status codes, and tests are updated to verify this fallback behavior. Feedback was provided regarding a potential data race in the new test due to unsynchronized access to a slice across goroutines, suggesting the use of a channel instead.

[gemini-code-assist]

The test TestQuery_FallsBackToControllerOn404 accesses the paths slice from both the HTTP server handler goroutine and the main test goroutine without explicit synchronization. Although there is a logical happens-before relationship via the HTTP round-trip, the Go race detector may flag this as a data race under -race because there is no explicit synchronization. Using a buffered channel to collect the request paths is a cleaner, safer, and idiomatic way to avoid any potential data races in tests.

	pathsChan := make(chan string, 2)
	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		pathsChan <- r.URL.Path
		if r.URL.Path == "/query/sql" {
			w.WriteHeader(http.StatusNotFound)
			_, _ = w.Write([]byte("not found"))
			return
		}
		_, _ = w.Write([]byte("{\"resultTable\":{}}"))
	}))
	defer srv.Close()

	c := New(srv.URL, &http.Client{Timeout: 5 * time.Second})
	if _, err := c.Query(context.Background(), "SELECT 1"); err != nil {
		t.Fatal(err)
	}
	close(pathsChan)
	var paths []string
	for p := range pathsChan {
		paths = append(paths, p)
	}
	want := []string{"/query/sql", "/sql"}
	if len(paths) != 2 || paths[0] != want[0] || paths[1] != want[1] {
		t.Errorf("request paths = %v; want %v", paths, want)
	}