fix(ts-sdk): expose Limitless watch helpers

[realfishsam]

Summary

• Add TypeScript Limitless.watchPrices(), watchUserPositions(), and watchUserTransactions() wrappers.
• Forward calls to the existing Limitless sidecar methods with the same args shape as the Python SDK.
• Add focused Jest coverage for method dispatch and optional callbacks.

Fixes #1297
Fixes #1298
Fixes #1299

Test Plan

• npm install
• npm test --workspace=pmxtjs -- limitless-watch-methods.test.ts --runInBand (passes; used a local uncommitted generated-client stub because this cron image has no checked-in sdks/typescript/generated output)
• npm run build --workspace=pmxtjs (passes with the same local generated-client stub)

Notes

• npm run generate --workspace=pmxtjs is blocked in this cron image because java is not installed for @openapitools/openapi-generator-cli; no generated artifacts were committed.

[realfishsam]

Verified after rebasing/merging current main from #1300: all GitHub checks are green; locally reran npm test --workspace=pmxtjs -- limitless-watch-methods.test.ts --runInBand (3 tests passed) and npm run build --workspace=pmxtjs (passed, using the local generated-client stub because Java/OpenAPI generator is unavailable in this cron image).