Fix cost tracking to use LiteLLM pricing database correctly

Add quality retention eval and fix linting for Python 3.12

feat(config): add OpenAI API URL override option

Enhance /stats endpoint and add comprehensive benchmarks

Fix mypy type errors in LiteLLM and OpenAI providers

Fix proxy passthrough routing to use SDK headers instead of User-Agent

Add CCR marker support to all compressors and fix retrieval

Enable LLMLingua and code-aware compression by default in proxy

Fix ZlibError by removing compression headers after httpx decompression

v0.2.2: Add CCR Response Handler, Context Tracker, and restructure docs

Add LLMLingua-2 opt-in support to proxy server

Fix all mypy type errors and flaky embedding test

Fix all ruff lint and format errors for CI

Publish headroom-ai v0.2.0 to PyPI with DevEx fixes

feat: Add CCR architecture, TOIN telemetry, and DevEx improvements

Prepare for OSS release v0.2.0