fix(services): retry malformed capability probes after the existing backoff

Rebased onto current main with review follow-ups folded in.

Co-Authored-By: Claude Sonnet 5.5 <[email protected]>

src/annotations/annotationEngine.test.mjs

@@ -313,7 +313,9 @@ test('retry: a plain HTTP 500 still exhausts the existing 8s/25s transient ladde
   t.mock.timers.enable({ apis: ['setTimeout', 'Date'], now: 100_000 });
   globalThis.window = { setTimeout: globalThis.setTimeout, clearTimeout: globalThis.clearTimeout };
   const requestTimes = [];
-  globalThis.fetch = async () => {
+  globalThis.fetch = async (url) => {
+    if (String(url).endsWith('/status'))
+      return Response.json({ configured: true });
     requestTimes.push(Date.now());
     return httpFailure(500);
   };