fix: replace JSON.stringify comparison with structural deep-equal for ProviderModelOptions

JSON.stringify is sensitive to property insertion order, so two
semantically identical ProviderModelOptions objects constructed with
keys in different orders would serialize to different strings. This
caused sameModelOptions to return false incorrectly, triggering
unnecessary Claude session restarts that cleared the resume cursor
and lost conversation context.

Replace with a recursive structural equality check that compares
objects by their defined (non-undefined) keys and values regardless
of key ordering.

Co-authored-by: Julius Marminge <juliusmarminge@users.noreply.github.com>

Author: cursoragent

apps/server/src/orchestration/Layers/ProviderCommandReactor.ts

@@ -75,10 +75,23 @@ const DEFAULT_RUNTIME_MODE: RuntimeMode = "full-access";
 const WORKTREE_BRANCH_PREFIX = "t3code";
 const TEMP_WORKTREE_BRANCH_PATTERN = new RegExp(`^${WORKTREE_BRANCH_PREFIX}\\/[0-9a-f]{8}$`);
 
+function structuralEqual(a: unknown, b: unknown): boolean {
+  if (a === b) return true;
+  if (a == null || b == null) return a === b;
+  if (typeof a !== typeof b) return false;
+  if (typeof a !== "object") return false;
+  const objA = a as Record<string, unknown>;
+  const objB = b as Record<string, unknown>;
+  const keysA = Object.keys(objA).filter((k) => objA[k] !== undefined);
+  const keysB = Object.keys(objB).filter((k) => objB[k] !== undefined);
+  if (keysA.length !== keysB.length) return false;
+  return keysA.every((key) => objB[key] !== undefined && structuralEqual(objA[key], objB[key]));
+}
+
 const sameModelOptions = (
   left: ProviderModelOptions | undefined,
   right: ProviderModelOptions | undefined,
-): boolean => JSON.stringify(left ?? null) === JSON.stringify(right ?? null);
+): boolean => structuralEqual(left ?? null, right ?? null);
 
 function isUnknownPendingApprovalRequestError(cause: Cause.Cause<ProviderServiceError>): boolean {
   const error = Cause.squash(cause);