docs: raise packages/README.md budget ceiling to 850

The group table legitimately gained one row for the new settings group;
the row itself is already condensed to the minimum. The intended raise
missed the merge commit because a pipeline swallowed the failing edit's
exit status.

scripts/doc-budgets.manifest.json

@@ -7,5 +7,5 @@
   "docs/testing.md": 1100,
   "examples/AGENTS.md": 310,
   "packages/AGENTS.md": 675,
-  "packages/README.md": 845
+  "packages/README.md": 850
 }