add changelog for v0.1.0 and v0.2.0

Keep-a-Changelog format with entries for the initial release, the
v0.2 feature drop (new compression techniques and sensitivity
analysis), and an Unreleased section tracking this stabilize-0.2
work.

Author: maskedsyntax

CHANGELOG.md

@@ -0,0 +1,63 @@
+# Changelog
+
+All notable changes to Comprexx are documented in this file.
+
+The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/),
+and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
+
+## [Unreleased]
+
+### Added
+- GitHub Actions CI workflow running `pytest` on Python 3.10, 3.11, 3.12 plus a
+  `ruff check` lint job.
+- `CHANGELOG.md` with history for v0.1.0 and v0.2.0.
+
+### Changed
+- Silenced the noisy `torch.ao.quantization is deprecated` warning inside the
+  PTQ dynamic and static stages. The underlying API is still used, with a
+  `TODO(v0.3)` marking the upcoming migration to `torchao.quantization`.
+- Fixed the package `__version__` to report `0.2.0` instead of the stale
+  `0.1.0` that shipped on PyPI.
+- Tightened the codebase against `ruff check` and added a per-file ignore
+  for `E741` in tests.
+
+## [0.2.0] - 2026-04-07
+
+### Added
+- **Unstructured pruning** stage: magnitude or random element-wise pruning
+  with global/local scope and optional gradual cubic schedule.
+- **N:M sparsity** stage: structured N-of-M sparsity (default 2:4) for
+  NVIDIA Ampere sparse tensor cores.
+- **Weight-only quantization** stage: group-wise INT4/INT8 with symmetric
+  or asymmetric scaling for Linear and Conv2d layers.
+- **Low-rank decomposition** stage: truncated SVD factorization of Linear
+  layers, with fixed rank-ratio or energy-threshold selection modes.
+- **Operator fusion** stage: Conv2d + BatchNorm2d folding via `torch.fx`
+  with graceful fallback on non-traceable models.
+- **Weight clustering** stage: per-layer k-means codebook clustering.
+- **`cx.analyze_sensitivity()`**: per-layer sensitivity probing via prune
+  or noise perturbation. Returns a `SensitivityReport` that ranks layers
+  by metric drop and can suggest `exclude_layers` above a threshold.
+- New techniques are wired through the recipe schema and loader, and
+  exported from `comprexx.stages`.
+
+### Tests
+- 163 passing (up from 91).
+
+## [0.1.0] - 2026-04-06
+
+Initial release.
+
+### Added
+- Model analysis and profiling via `cx.analyze()`.
+- Structured pruning with L1/L2/random criteria and global/local scope.
+- Post-training dynamic and static INT8 quantization.
+- ONNX export with manifest and optional `onnxruntime` validation.
+- Recipe-driven pipelines (YAML) validated via Pydantic.
+- CLI commands: `comprexx analyze`, `compress`, `export`.
+- Accuracy guards with halt/warn actions.
+- Per-stage compression reports persisted under `comprexx_runs/`.
+
+[Unreleased]: https://github.com/cachevector/comprexx/compare/v0.2.0...HEAD
+[0.2.0]: https://github.com/cachevector/comprexx/compare/v0.1.0...v0.2.0
+[0.1.0]: https://github.com/cachevector/comprexx/releases/tag/v0.1.0