chore: complete v1.8.0 Quick Mode milestone

Archived:
- milestones/v1.8.0-ROADMAP.md
- milestones/v1.8.0-REQUIREMENTS.md

Deleted (fresh for next milestone):
- ROADMAP.md
- REQUIREMENTS.md

Updated:
- MILESTONES.md (new entry)
- PROJECT.md (requirements → Validated)
- STATE.md (reset for next milestone)

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

.planning/MILESTONES.md

@@ -0,0 +1,28 @@
+# Project Milestones: GSD
+
+## v1.8.0 Quick Mode (Shipped: 2026-01-19)
+
+**Delivered:** Fast-path command (`/gsd:quick`) for executing small tasks with full GSD guarantees but 50-70% fewer tokens.
+
+**Phases completed:** 1-2 (3 plans total)
+
+**Key accomplishments:**
+
+- Created `/gsd:quick` command with interactive prompting and directory setup
+- Implemented gsd-planner and gsd-executor spawning for quick mode
+- Added STATE.md Quick Tasks Completed table integration
+- Documented quick mode in help.md, README.md, and GSD-STYLE.md
+- Established quick task directory structure (`.planning/quick/NNN-slug/`)
+
+**Stats:**
+
+- 34 files created/modified
+- +1,129/-379 lines
+- 2 phases, 3 plans, 2 quick tasks
+- Same-day completion (2026-01-19)
+
+**Git range:** `2b36394` → `7692ebd` (1.8.0)
+
+**What's next:** Codebase Intelligence System
+
+---