docs(phase-1): add validation strategy

.planning/phases/01-foundation/01-VALIDATION.md

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+---
+phase: 1
+slug: foundation
+status: draft
+nyquist_compliant: false
+wave_0_complete: false
+created: 2026-03-10
+---
+
+# Phase 1 — Validation Strategy
+
+> Per-phase validation contract for feedback sampling during execution.
+
+---
+
+## Test Infrastructure
+
+| Property | Value |
+|----------|-------|
+| **Framework** | No test framework — manual visual validation only |
+| **Config file** | none — single HTML file, no npm/testing setup |
+| **Quick run command** | Open `index.html` in browser; visually confirm ball bounces, paddle responds |
+| **Full suite command** | Test on Retina/HiDPI device; test on 120 Hz display; test on 30 Hz device |
+| **Estimated runtime** | ~2 minutes |
+
+---
+
+## Sampling Rate
+
+- **After every task commit:** Open `index.html` in browser; visually confirm the feature just implemented works
+- **After every plan wave:** Full visual validation on HiDPI device, confirm all implemented features still work together
+- **Before `/gsd:verify-work`:** All 6 success criteria must be manually confirmed green
+- **Max feedback latency:** ~120 seconds (open browser, observe, confirm)
+
+---
+
+## Per-Task Verification Map
+
+| Task ID | Plan | Wave | Requirement | Test Type | Automated Command | File Exists | Status |
+|---------|------|------|-------------|-----------|-------------------|-------------|--------|
+| 1-01-01 | 01 | 1 | CORE-01 | Manual visual | Open `index.html`, observe ball moves and bounces | ✅ After Phase 1 | ⬜ pending |
+| 1-01-02 | 01 | 1 | VFX-05 | Manual visual | Open on Retina device; graphics should be sharp | ✅ After Phase 1 | ⬜ pending |
+| 1-01-03 | 01 | 1 | CORE-07 | Manual visual | Press W/S; paddle moves smoothly without input lag | ✅ After Phase 1 | ⬜ pending |
+| 1-01-04 | 01 | 1 | CORE-03 | Manual visual | Hit ball at top/center/bottom of paddle; angle should change | ✅ After Phase 1 | ⬜ pending |
+| 1-01-05 | 01 | 1 | CORE-04 | Manual visual + console | Rally 10+ times; confirm speed increases; check `console.log(ball.speed)` | ✅ After Phase 1 | ⬜ pending |
+| 1-01-06 | 01 | 1 | CORE-02 | Manual visual | Paddle deflects ball correctly off all zones | ✅ After Phase 1 | ⬜ pending |
+
+*Status: ⬜ pending · ✅ green · ❌ red · ⚠️ flaky*
+
+---
+
+## Wave 0 Requirements
+
+*Existing infrastructure covers all phase requirements.*
+
+No automated test framework needed for Phase 1. The project is a single HTML file with vanilla JS — manual visual validation is appropriate and sufficient for this phase's prototype nature.
+
+---
+
+## Manual-Only Verifications
+
+| Behavior | Requirement | Why Manual | Test Instructions |
+|----------|-------------|------------|-------------------|
+| Ball moves continuously and bounces off top/bottom walls | CORE-01 | Visual physics — no DOM assertion possible | Open `index.html`, observe ball moves at all times and bounces off top/bottom |
+| Player 1 controls paddle with W/S keys | CORE-07 | Requires human keyboard input | Press W to move up, S to move down; confirm smooth, immediate response |
+| Ball angle changes based on paddle hit zone | CORE-03 | Requires observing trajectory variation | Hit ball at top, middle, and bottom of paddle; confirm different angles result |
+| Ball speed increases over match | CORE-04 | Requires sustained play session | Rally 10+ times; speed should noticeably increase; verify with `console.log(ball.speed)` |
+| Canvas renders sharply on Retina/HiDPI | VFX-05 | Requires HiDPI display hardware | Open on Retina device; compare with devicePixelRatio=1 display to confirm sharpness |
+| Paddle deflects ball | CORE-02 | Visual interaction — no DOM assertion | Move paddle into ball's path; confirm ball bounces off paddle surface |
+
+---
+
+## Validation Sign-Off
+
+- [ ] All tasks have `<automated>` verify or Wave 0 dependencies
+- [ ] Sampling continuity: no 3 consecutive tasks without automated verify
+- [ ] Wave 0 covers all MISSING references
+- [ ] No watch-mode flags
+- [ ] Feedback latency < 120s
+- [ ] `nyquist_compliant: true` set in frontmatter
+
+**Approval:** pending