feat: consolidate CLI and add structured logging

[martinffx]

Major architectural improvements:

• Consolidated internal/cli/ (8 files) into single internal/cli.go
• Moved business logic to domain packages (daemon.LaunchWithClaude, daemon.ShowLastLines, daemon.FollowLogs)
• Added structured logging with slog and log rotation via lumberjack
• Made 'athena' launch daemon + Claude Code by default
• Made 'athena logs' tail by default (--follow=true)

Breaking changes:

• Removed JSON config format support (YAML-only)
• Removed wrapper scripts from release workflow
• Changed default behavior: 'athena' now runs 'athena code' functionality

Configuration improvements:

• Added logging flags (--log-format, --log-file)
• Updated all docs to reference YAML-only config
• Simplified config precedence: CLI → YAML → env → defaults

Release workflow improvements:

• Removed 200+ lines of wrapper script generation
• Simplified installation with integrated daemon management
• Updated release documentation and examples

Architecture benefits:

• Single source of truth for CLI commands
• Clear separation: CLI orchestrates, domains implement
• Better testability with domain functions
• Follows single-file organization standard

All tests passing (109 tests across 6 packages)
Security scan clean with govulncheck

🤖 Generated with Claude Code

Description

Brief description of the changes in this PR.

Type of Change

• 🐛 Bug fix (non-breaking change which fixes an issue)
• ✨ New feature (non-breaking change which adds functionality)
• 💥 Breaking change (fix or feature that would cause existing functionality to not work as expected)
• 📚 Documentation update
• 🔧 Configuration change
• ♻️ Code refactoring (no functional changes)

Testing

• I have run make check locally and all checks pass
• I have tested the changes manually
• I have added tests that prove my fix is effective or that my feature works

Checklist

• My code follows the project's style guidelines (enforced by make fmt and make lint)
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• My changes generate no new warnings
• Any dependent changes have been merged and published

Configuration Changes

If this PR changes configuration options:

• I have updated example config files (openrouter.example.yml, openrouter.example.json, .env.example)
• I have updated the README.md with new configuration options
• I have updated CLAUDE.md if the changes affect development workflow

Additional Notes

Any additional information, context, or screenshots that would be helpful for reviewers.