fix(structured): narrow validateJsonSchemaSafe to RangeError-only + drop unused import (review fold-in)

Reviewer of #184: the catch-all would silently mask a future genuine bug (e.g. a
TypeError from a malformed schema) as a validation miss. Narrowed to
`if (e instanceof RangeError) return [...]; throw e;` so only the #181 deep-nesting
overflow becomes a refusal; any other throw surfaces at error level as before. +1
test proving a non-RangeError (required:42 → TypeError) re-throws. Dropped the now-
unused raw `validateJsonSchema` import from server.mjs. Merged current main (incl.
#183) so CI runs the true post-merge tree. Suite 433/0.

Co-Authored-By: Claude <claude-opus-4-8> <noreply@anthropic.com>

test-features.mjs

@@ -4405,6 +4405,12 @@ test("validateJsonSchemaSafe: well-formed value passes through unchanged (byte-i
   assert.deepEqual(validateJsonSchemaSafe({ name: "a" }, schema), validateJsonSchema({ name: "a" }, schema)); // error case matches too
 });
 
+test("validateJsonSchemaSafe: re-throws a non-RangeError so genuine bugs aren't masked as a validation miss", () => {
+  // A schema whose `required` is a non-iterable makes the inner validator throw a TypeError — that's
+  // a real bug, not a deep-value overflow, and must surface (not be swallowed as "did not validate").
+  assert.throws(() => validateJsonSchemaSafe({ x: 1 }, { type: "object", required: 42 }), (e) => !(e instanceof RangeError));
+});
+
 test("validateJsonSchema: valid object passes", () => {
   assert.deepEqual(validateJsonSchema({ name: "a", age: 3 }, { type: "object", required: ["name", "age"], properties: { name: { type: "string" }, age: { type: "integer" } } }), []);
 });