📝 Rework documentation for addon system and native CLI

[renardeinside]

Summary

• Addon system: Replace all --template references with composable --addons system across docs, CLI reference, and terminal demos
• Native CLI install: Replace uvx --index ... and uv run apx with curl | sh / irm | iex installation and direct apx commands
• Dependency table: Align Rust crate table in README with actual cargo tree (removed 4 stale crates, added 19 new ones)
• Bun bundling: Remove "bundled Bun" language while keeping Bun as a listed technology
• Template files: Update all MCP configs, assistant rules (Cursor, VSCode, Claude, Codex), and scaffolding templates to use apx commands
• Terminal demos: Show realistic install.sh output + addon multi-select UI with scrollable overflow fix

Test plan

• Verify docs site builds: cd docs && bun run build
• Check all internal links resolve correctly
• Confirm terminal demo renders with scrollable content
• Verify apx init generates correct MCP configs with "command": "apx"

🤖 Generated with Claude Code