fix(hyperliquid): submit/cancel trading-path bugs (silent error, wrong asset id, msgpack int64)

[realfishsam]

Summary

Three real HL bugs surfaced by live ground-truth trading verification against a funded mainnet wallet:

1. submitOrder silently swallowed HL rejections

When HL returned statuses[0].error (e.g. "Order must have minimum value of 10 USDC"), the SDK reported status='filled', id='unknown' — fake success. The order didn't exist, but the caller had no way to know.

→ Now raises a typed PmxtError carrying HL's message. Also handles the filled branch correctly (was checked but never populated price or oid in the response).

2. cancelOrder hardcoded a: 0 (asset id)

Every cancel signed an action with cancels: [{a: 0, o: <oid>}]. HL rejected with User or API Wallet 0xfaf6… does not exist because the action hash with the wrong asset recovers a different signer address.

→ Now looks up the open order to derive the real asset id via encodeAssetId. Throws typed Order not found when the supplied oid isn't open.

3. msgpack int64 vs uint64 — one byte off

msgpackr encodes positive BigInts as int64 (0xd3); HL's server (Python msgpack) encodes the same values as uint64 (0xcf). Identical bit pattern, different type byte → action hash mismatch → signature recovers to wrong address. Only manifested on cancel because order actions don't carry BigInt fields; cancel does (oid).

→ Added fixInt64ToUint64 post-processor. HL actions never carry negative ints (oids, nonces, asset ids are all ≥ 0), so flipping d3 → cf when the following byte is < 0x80 is safe and produces byte-identical encoding to Python msgpack.

Verified end-to-end against live wallet 0xcb85…

createOrder (BUY 100 @ \$0.10, hl-outcome-553)
  → id=476019713300 status=open
fetch_open_orders → contains the order
cancelOrder(id) → status=canceled
fetch_open_orders → empty
cancelOrder('999999999999') → typed PmxtError 'Order not found'

No funds were lost in verification (orders rested far below market and were cancelled within seconds).

Test plan

• Trading on HL succeeds with typed error responses
• Cancel of open orders works
• Cancel of stale/fake order id raises typed PmxtError