test: add explicit /api/graphql proxy coverage in handler test

Agent-Logs-Url: https://github.com/github/gh-aw-mcpg/sessions/c6b2a362-0e12-4612-9786-e6d4c9c0687c

Co-authored-by: lpcox <15877973+lpcox@users.noreply.github.com>

Author: Copilot

internal/proxy/handler_test.go

@@ -195,8 +195,10 @@ func TestServeHTTP_GraphQLPreservesQueryString(t *testing.T) {
 		wantPath string
 	}{
 		{name: "graphql path", path: "/graphql?foo=bar", wantPath: "/graphql?foo=bar"},
-		{name: "ghes api graphql path", path: "/api/graphql?foo=bar", wantPath: "/graphql?foo=bar"},
-		{name: "gh host prefixed graphql path", path: "/api/v3/graphql?foo=bar", wantPath: "/graphql?foo=bar"},
+		{name: "ghes api graphql path", path: "/api/graphql", wantPath: "/graphql"},
+		{name: "ghes api graphql path with query", path: "/api/graphql?foo=bar", wantPath: "/graphql?foo=bar"},
+		{name: "gh host prefixed graphql path", path: "/api/v3/graphql", wantPath: "/graphql"},
+		{name: "gh host prefixed graphql path with query", path: "/api/v3/graphql?foo=bar", wantPath: "/graphql?foo=bar"},
 	}
 
 	for _, tt := range tests {