fix(consult): treat pinched answers as failed and restore reply actions

Incomplete Flash generations were billed as completed consultations. Fail
those runs, keep the partial text, and reuse the rectification like/copy/rerun
bar on ordinary chat replies.

Co-authored-by: Cursor <cursoragent@cursor.com>

frontend/tests/agent-observability.test.ts

@@ -145,6 +145,10 @@ test("error normalization never records arbitrary exception messages", () => {
     toAgentObservabilityErrorCode(new Error("runtime_contract_incomplete")),
     "runtime_contract_incomplete",
   );
+  assert.equal(
+    toAgentObservabilityErrorCode(new Error("answer_truncated")),
+    "answer_truncated",
+  );
   assert.equal(
     toAgentObservabilityErrorCode(new Error("/opt/internal/users/alice.json")),
     "calculation_failed",