Polish bundle: docs cleanup (stale ROADMAP entry, missing PyPI classifiers) #272

Summary

Small docs / metadata cleanup bundled for a single PR.

Item 1 — ROADMAP carries a stale "Unreleased (post-v2.2.0)" entry

- **Unreleased (post-v2.2.0)** — WS reliability + auth polish batch.
  Shipped under v2.3.0 below.

Readers scanning the Shipped list see an "Unreleased" bullet immediately under v2.4.0, implying ongoing in-flight work that's actually already on PyPI.

Location: ROADMAP.md:14-16.

Fix: Delete the bullet — v2.3.0 is already listed below it as a normal shipped entry.

Item 2 — pyproject.toml is missing Framework :: AsyncIO and Financial Trove classifiers

PyPI faceted search by Framework :: AsyncIO and Topic :: Office/Business :: Financial :: Investment misses kalshi-sdk despite the package shipping an AsyncKalshiClient and being a real-money trading SDK. Lower discoverability for the exact audience the SDK is built for.

Location: pyproject.toml:10-18.

Fix: Add "Framework :: AsyncIO", "Topic :: Office/Business :: Financial :: Investment", and "Operating System :: OS Independent" to the classifiers list.

Severity & category

low / polish, docs