Comment on: ADR-006: Extension Modularization & Install Infrastructure

## Implementation Plan: Extension Modularization **Full plan:** [`.plans/IMPLEMENTATION-PLAN-extension-modularization.md`](https://github.com/jeremymcs/gsd-2/blob/feat/extension-system-analysis/.plans/IMPLEMENTATION-PLAN-extension-modularization.md) ### Summary **Goal:** Make GSD2 lightweight out of the box by extracting optional features into installable extensions, reducing core footprint from 177K LOC to ~15-20K LOC and `node_modules` from 842 MB to ~450 MB. ### Phases | Phase | Description | Effort | Risk | Dependencies | |-------|-------------|--------|------|-------------| | **0** | Foundation — Dependency Cleanup & Architecture Fixes | Small (1-2 sessions) | Low | None | | **1** | Extension Install Infrastructure (`gsd extensions install`) | Medium (2-3 sessions) | Medium | None | | **2** | Extract Self-Contained Extensions (Tier 1) — 8 extensions | Medium (2-3 sessions) | Low | Phase 1 | | **3** | Preferences Service & Tier 2 Extraction — 6 extensions | Medium-Large (3-4 s...