docs: update CHANGELOG with v0.2.0 + plugin additions

docs/changelog/CHANGELOG.md

@@ -5,6 +5,21 @@ All notable changes to Salior are documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [0.2.0] — 2026-05-11
+
+### Added
+
+- **4 built-in plugins** (`plugins/`)
+  - `llm_batcher/` — Batch multiple LLM calls into one request (cost + speed)
+  - `backtest_engine/` — Vectorized historical backtesting on TimescaleDB candles
+  - `rl_trainer/` — PPO reinforcement learning agent training (GPU node required)
+  - `ml_predictor/` — scikit-learn signal enhancement model
+
+### Changed
+
+- `plugins/` directory now populated (was empty in v0.1.0)
+- `CHANGELOG.md` added at `docs/changelog/CHANGELOG.md`
+
 ## [0.1.0] — 2026-05-11
 
 ### Added
@@ -65,7 +80,6 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Known Limitations
 
 - `exec_agent` is a stub for live trading — requires HL API wallet private key (secp256k1 ECDSA)
-- `plugins/` directory is empty (llm_batcher, backtest_engine, rl_trainer not yet implemented)
 - Dashboard web UI not yet built
 - No risk agent (`agents/risk/`)
 - `place_order` MCP tool requires wallet approval flow (frontend not wired yet)