docs(13): add research and validation strategy

.planning/phases/13-setup-impact-preview/13-VALIDATION.md

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+---
+phase: 13
+slug: setup-impact-preview
+status: draft
+nyquist_compliant: false
+wave_0_complete: false
+created: 2026-03-17
+---
+
+# Phase 13 — Validation Strategy
+
+> Per-phase validation contract for feedback sampling during execution.
+
+---
+
+## Test Infrastructure
+
+| Property | Value |
+|----------|-------|
+| **Framework** | bun test (built-in) |
+| **Config file** | bunfig.toml |
+| **Quick run command** | `bun test` |
+| **Full suite command** | `bun test` |
+| **Estimated runtime** | ~5 seconds |
+
+---
+
+## Sampling Rate
+
+- **After every task commit:** Run `bun test`
+- **After every plan wave:** Run `bun test`
+- **Before `/gsd:verify-work`:** Full suite must be green
+- **Max feedback latency:** 5 seconds
+
+---
+
+## Per-Task Verification Map
+
+| Task ID | Plan | Wave | Requirement | Test Type | Automated Command | File Exists | Status |
+|---------|------|------|-------------|-----------|-------------------|-------------|--------|
+| 13-01-01 | 01 | 1 | IMPC-01 | unit | `bun test` | ❌ W0 | ⬜ pending |
+| 13-01-02 | 01 | 1 | IMPC-02 | unit | `bun test` | ❌ W0 | ⬜ pending |
+| 13-01-03 | 01 | 1 | IMPC-03 | unit | `bun test` | ❌ W0 | ⬜ pending |
+| 13-01-04 | 01 | 1 | IMPC-04 | unit | `bun test` | ❌ W0 | ⬜ pending |
+
+*Status: ⬜ pending · ✅ green · ❌ red · ⚠️ flaky*
+
+---
+
+## Wave 0 Requirements
+
+- [ ] Test stubs for IMPC-01 through IMPC-04 impact delta computation
+- [ ] Test fixtures for setup items and thread candidates with weight/price data
+
+*If none: "Existing infrastructure covers all phase requirements."*
+
+---
+
+## Manual-Only Verifications
+
+| Behavior | Requirement | Why Manual | Test Instructions |
+|----------|-------------|------------|-------------------|
+| Setup dropdown renders in thread header | IMPC-01 | Visual/UI placement | Open a thread, verify dropdown appears with all setups listed |
+| Delta labels display correctly (add vs replace) | IMPC-03 | Visual formatting | Select setup with no category match, verify "add" label |
+| Missing weight shows "-- (no weight data)" | IMPC-04 | Visual indicator | Add candidate with no weight, verify placeholder text |
+
+---
+
+## 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 < 5s
+- [ ] `nyquist_compliant: true` set in frontmatter
+
+**Approval:** pending