Pre-release fixes and polish for open source launch

Fixed critical issues identified in code review:
- Fixed invalid Go version (1.25.2 → 1.21) in go.mod
- Fixed unchecked error in import.go JSON unmarshaling
- Fixed unchecked error returns in test cleanup (export_import_test.go, import_collision_test.go)
- Removed duplicate test code in dependencies_test.go via helper function

Added release infrastructure:
- Added 'bd version' command with JSON output support
- Created comprehensive CHANGELOG.md following Keep a Changelog format
- Updated README.md with clear alpha status warnings

All tests passing. Ready for public repository opening.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

CHANGELOG.md

@@ -0,0 +1,113 @@
+# Changelog
+
+All notable changes to the beads 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).
+
+## [Unreleased]
+
+### Fixed
+- Fixed unchecked error in import.go when unmarshaling JSON
+- Fixed unchecked error returns in test cleanup code
+- Removed duplicate test code in dependencies_test.go
+- Fixed Go version in go.mod (was incorrectly set to 1.25.2)
+
+### Added
+- Added `bd version` command to display version information
+- Added CHANGELOG.md to track project changes
+
+## [0.9.0] - 2025-10-12
+
+### Added
+- **Collision Resolution System**: Automatic ID remapping for import collisions
+  - Reference scoring algorithm to minimize updates during remapping
+  - Word-boundary regex matching to prevent false replacements
+  - Automatic updating of text references and dependencies
+  - `--resolve-collisions` flag for safe branch merging
+  - `--dry-run` flag to preview collision detection
+- **Export/Import with JSONL**: Git-friendly text format
+  - Dependencies embedded in JSONL for complete portability
+  - Idempotent import (exact matches detected)
+  - Collision detection (same ID, different content)
+- **Ready Work Algorithm**: Find issues with no open blockers
+  - `bd ready` command shows unblocked work
+  - `bd blocked` command shows what's waiting
+- **Dependency Management**: Four dependency types
+  - `blocks`: Hard blocker (affects ready work)
+  - `related`: Soft relationship
+  - `parent-child`: Epic/subtask hierarchy
+  - `discovered-from`: Track issues discovered during work
+- **Database Discovery**: Auto-find database in project hierarchy
+  - Walks up directory tree like git
+  - Supports `$BEADS_DB` environment variable
+  - Falls back to `~/.beads/default.db`
+- **Comprehensive Documentation**:
+  - README.md with 900+ lines of examples and FAQs
+  - CLAUDE.md for AI agent integration patterns
+  - SECURITY.md with security policy and best practices
+  - TEXT_FORMATS.md analyzing JSONL approach
+  - EXTENDING.md for database extension patterns
+  - GIT_WORKFLOW.md for git integration
+- **Examples**: Real-world integration patterns
+  - Python agent implementation
+  - Bash agent script
+  - Git hooks for automatic export/import
+  - Branch merge workflow with collision resolution
+  - Claude Desktop MCP integration (coming soon)
+
+### Changed
+- Switched to JSONL as source of truth (from binary SQLite)
+- SQLite database now acts as ephemeral cache
+- Issue IDs generated with numerical max (not alphabetical)
+- Export sorts issues by ID for consistent git diffs
+
+### Security
+- SQL injection protection via allowlisted field names
+- Input validation for all issue fields
+- File path validation for database operations
+- Warnings about not storing secrets in issues
+
+## [0.1.0] - Initial Development
+
+### Added
+- Core issue tracking (create, update, list, show, close)
+- SQLite storage backend
+- Dependency tracking with cycle detection
+- Label support
+- Event audit trail
+- Full-text search
+- Statistics and reporting
+- `bd init` for project initialization
+- `bd quickstart` interactive tutorial
+
+---
+
+## Version History
+
+- **0.9.0** (2025-10-12): Pre-release polish and collision resolution
+- **0.1.0**: Initial development version
+
+## Upgrade Guide
+
+### Upgrading to 0.9.0
+
+No breaking changes. The JSONL export format is backward compatible.
+
+If you have issues in your database:
+1. Run `bd export -o .beads/issues.jsonl` to create the text file
+2. Commit `.beads/issues.jsonl` to git
+3. Add `.beads/*.db` to `.gitignore`
+
+New collaborators can clone the repo and run:
+```bash
+bd import -i .beads/issues.jsonl
+```
+
+The SQLite database will be automatically populated from the JSONL file.
+
+## Future Releases
+
+See open issues tagged with milestone markers for planned features in upcoming releases.
+
+For version 1.0, see: `bd dep tree bd-8` (the 1.0 milestone epic)