release: bump version to v0.2.0

- Update version.go to 0.2.0
- Add comprehensive CHANGELOG.md entry for v0.2.0 (178 commits)
- Add gt info command with --whats-new flag for agent-relevant changes

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

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

internal/cmd/version.go

@@ -11,7 +11,7 @@ import (
 
 // Version information - set at build time via ldflags
 var (
-	Version = "0.1.2"
+	Version = "0.2.0"
 	// Build can be set via ldflags at compile time
 	Build = "dev"
 	// Commit and Branch - the git revision the binary was built from (optional ldflag)