fix(security): bound response bodies in secureFetchWithPinnedIP by default (#6169)

secureFetchWithPinnedIP only capped a response body when the caller passed
maxResponseBytes; with the option absent the body streamed into an unbounded
Buffer.concat. Several tool proxies whose target host is user-supplied
(Jupyter, ClickHouse, Grafana, 1Password Connect) and the RSS poller called it
without that option, so an attacker-controlled server answering with an endless
chunked body could grow the shared process heap until it was OOM-killed.

Make the cap fail-safe: default to 100MB (and treat a non-positive value as the
default) so there is no unlimited mode, then pass tighter explicit caps at the
user-supplied-host sites.

Responses that carry no body (HEAD, 204, 304) are exempted from the
content-length pre-check — they advertise the resource size as metadata, which
would otherwise spuriously fail a HEAD probe of a large file or an RSS
conditional-GET 304.

packages/testing/src/mocks/input-validation.mock.ts

@@ -29,6 +29,8 @@ export const inputValidationMockFns = {
  * ```
  */
 export const inputValidationMock = {
+  DEFAULT_MAX_RESPONSE_BYTES: 100 * 1024 * 1024,
+  MAX_JSON_API_RESPONSE_BYTES: 10 * 1024 * 1024,
   validateUrlWithDNS: inputValidationMockFns.mockValidateUrlWithDNS,
   validateAndPinProxyUrl: inputValidationMockFns.mockValidateAndPinProxyUrl,
   validateDatabaseHost: inputValidationMockFns.mockValidateDatabaseHost,