chore: Move internal MD files to docs/ directory

Moved to docs/:
- CHANGELOG.md (duplicate of changelog/)
- IMPLEMENTATION_SUMMARY.md
- STRATEGY_BUILDER_DESIGN.md
- TODO.md
- QWEN.md (AI assistant context only)

Root MD files (GitHub standards only):
- README.md (main documentation)
- LICENSE (legal requirement)
- SECURITY.md
- CODE_OF_CONDUCT.md
- CONTRIBUTING.md
- SUPPORT.md
- ATTRIBUTION.md

Root directory: 31 files → 29 files

CHANGELOG.md

@@ -1,34 +0,0 @@
-# Changelog
-
-All notable changes to Predix will be 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).
-
-## Releases
-
-### Version 1.0.0 (2026-04-02)
-
-**Initial Release - EURUSD Trading Agent**
-
-📄 **Detailed release notes:** [changelog/v1.0.0.md](changelog/v1.0.0.md)
-
-**Highlights:**
-- ✨ 110+ EURUSD factors generated autonomously
-- 🧠 Multi-agent debate system (Bull/Bear/Neutral)
-- 📊 Backtesting engine with IC, Sharpe, Drawdown
-- 🗄️ SQLite database for tracking results
-- ⚖️ Risk management with correlation analysis
-- 📱 Web + CLI dashboards
-- ✅ 97 tests with 98.77% coverage
-- 📚 Comprehensive documentation
-
----
-
-## Historical Changes (from RD-Agent upstream)
-
-For earlier changes inherited from the RD-Agent project, see the [upstream changelog](https://github.com/microsoft/RD-Agent/blob/main/CHANGELOG.md).
-
----
-
-## [Unreleased]