fix(ts-sdk): make hosted errors catchable by base class

[realfishsam]

Summary

• Fixes TypeScript SDK hosted error detection so concrete hosted subclasses satisfy instanceof HostedTradingError.
• Keeps existing semantic parent classes (InvalidApiKey as AuthenticationError, InsufficientEscrowBalance as InsufficientFunds, etc.) while making the hosted base catch work via Symbol.hasInstance and the existing isHostedError marker.

Fixes #1411

Test Plan

• npm install
• npm test --workspace=pmxtjs -- hosted-error-mapping.test.ts --runInBand
• git diff --check

Notes

• npm run build --workspace=pmxtjs is blocked in this checkout by missing generated TypeScript SDK artifacts: ../generated/src/index.js imported by pmxt/client.ts and pmxt/server-manager.ts.