refactor: Create CHANGELOG.md documenting version history and recent improvements

Author: leocavalcante

CHANGELOG.md

@@ -0,0 +1,75 @@
+# Changelog
+
+All notable changes to this project 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).
+
+## [1.0.0] - 2026-01-18
+
+### Added
+- **Metrics System** - Track cycles, tasks, token usage, and estimated costs
+  - `--status` CLI flag to display metrics summary without starting the loop
+  - `--metrics-reset` CLI flag to reset all metrics to default values with confirmation
+  - Comprehensive metrics tracking in `metrics.json` including token counts and cost estimation
+- **Token Usage Tracking** - Enhanced token tracking with accurate model cost estimation
+  - Support for all major model providers: Claude (Anthropic), GPT (OpenAI), Gemini (Google)
+  - Automatic cost calculation based on current market pricing
+  - Token tracking integration in plan and build phases
+- **Session Statistics** - Detailed session-level statistics including:
+  - Input and output token counts per operation
+  - Session duration tracking
+  - Summary logging at end of each cycle
+- **Git Integration Improvements**
+  - Proper escaping of special characters in commit messages
+  - `hasUnpushedCommits()` function to detect unpushed changes
+  - Better handling of git operations with improved error messages
+- **Ideas Queue Enhancements** - Improved reliability and crash safety
+  - Idea backup before processing
+  - Idea tracking in state for crash recovery
+  - Auto-cleanup of empty/invalid ideas
+- **Comprehensive Test Coverage** - Full test suite for all modules
+  - 443 tests covering CLI, build, git, metrics, eval, and more
+  - High confidence in code reliability
+
+### Changed
+- **Terminology Update** - Renamed "Planning" to "Plan" throughout codebase
+  - Updated documentation and variable names for consistency
+  - Improved naming clarity in phase descriptions
+- **Build Phase Naming** - Renamed "builder" module to "build"
+  - More concise and idiomatic naming
+  - Updated all related imports and test files
+- **Evaluation Phase** - Renamed "evaluation" to "eval"
+  - Shorter terminology for consistency with phase naming
+  - Updated all functions and types accordingly
+- **Directory Structure** - Standardized on `.opencode/opencoder/` directory
+  - All OpenCoder artifacts stored under this path
+  - Improved organization and clarity
+
+### Fixed
+- Improved idea handling reliability with better crash safety mechanisms
+- Better null/undefined handling in message part extraction
+- Special character escaping in git commit messages
+- State validation for invalid phase names
+
+### Technical Improvements
+- Exponential backoff retry mechanism for transient failures
+- Cycle timeout/watchdog mechanism to prevent infinite loops
+- Visual feedback for AI thinking and tool usage during development
+- Improved logger output with file change notifications
+- Enhanced FS utilities for better file operations
+
+## [0.1.0] - 2026-01-16
+
+### Added
+- Initial OpenCoder release
+- Autonomous development loop with three phases: Plan, Build, Eval
+- Ideas queue system for directing AI toward specific tasks
+- OpenCode SDK integration with real-time event streaming
+- Two-model architecture (separate models for plan and build)
+- Live output streaming of AI thinking and tool calls
+- State persistence for resumable development cycles
+- Automatic git operations (commit and push)
+- Plan history archival
+- Comprehensive logging and metrics
+