docs: add changelog (v0.1.0, v0.2.0)

Author: blackwell-systems

CHANGELOG.md

@@ -0,0 +1,18 @@
+# Changelog
+
+## v0.2.0 (2026-06-03)
+
+- `encode_generic`: encode arbitrary Python values into GCF tabular format
+- Tabular encoding: positional rows with pipe separators, section headers, nested field support
+- Uniform array detection with 70% key overlap threshold
+
+## v0.1.0 (2026-06-03)
+
+- Initial release
+- `encode` / `decode`: full GCF round-trip
+- `encode_with_session`: session deduplication (92.7% savings by 5th call)
+- `encode_delta`: delta encoding for re-queries (81.2% savings)
+- Thread-safe `Session` class
+- 16 kind abbreviations
+- CLI: `gcf encode`, `gcf decode`, `gcf stats`
+- Type hints, Python 3.9+, zero runtime dependencies