Tier 2: cap response body size to prevent OOM from a hostile/misconfigured endpoint

[MarketDataApp]

Tier 2 per SECURITY.md — a compatibility-affecting change; needs maintainer approval before merge. Surfaced by the security review behind #39.

Problem

HttpDispatcher.send reads the entire response body with BodyHandlers.ofByteArray() (HttpDispatcher.java:81) — no size cap, no Content-Length sanity check. The §10 controls bound time (99s/2s), not bytes. The body is then amplified: tree-parsed into a JsonNode (2nd copy) and body().clone()'d in AbstractMarketDataResponse (3rd copy).

A hostile/misconfigured endpoint can stream a multi-GB body → process-wide OutOfMemoryError the consumer cannot catch or defend against.

Trigger: requires a compromised endpoint, a baseUrl pointed at an attacker, or MITM (defeated by TLS) — not reachable against the real API over HTTPS. Robustness/DoS hardening, not a remote 0-day.

Proposed fix (needs approval — Tier 2)

• Add a response-body size ceiling (a bounded BodySubscriber that aborts past N bytes, and/or reject when Content-Length exceeds a limit), surfaced as a controlled ParseError/NetworkError.
• Separately, pin Jackson StreamReadConstraints explicitly so a future Jackson downgrade below 2.15 can't silently re-open the long-number/long-string/deep-nesting DoS defaults we currently rely on.

Why Tier 2

A size ceiling is a new default limit that could reject unusually large but legitimate responses — needs a deliberate cap value.