docs(phase-02): add validation strategy

.planning/phases/02-tier-1-2-providers/02-VALIDATION.md

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+---
+phase: 2
+slug: tier-1-2-providers
+status: draft
+nyquist_compliant: false
+wave_0_complete: false
+created: 2026-04-05
+---
+
+# Phase 2 — Validation Strategy
+
+> Per-phase validation contract for feedback sampling during execution.
+
+---
+
+## Test Infrastructure
+
+| Property | Value |
+|----------|-------|
+| **Framework** | go test (stdlib) + testify v1.x assertions |
+| **Config file** | none — existing from Phase 1 |
+| **Quick run command** | `go test ./pkg/providers/... -short` |
+| **Full suite command** | `go test ./... -v -count=1` |
+| **Estimated runtime** | ~5 seconds |
+
+---
+
+## Sampling Rate
+
+- **After every task commit:** Run `go test ./pkg/providers/... -short`
+- **After every plan wave:** Run `go test ./... -v -count=1`
+- **Before `/gsd:verify-work`:** Full suite must be green
+- **Max feedback latency:** 10 seconds
+
+---
+
+## Per-Task Verification Map
+
+| Task ID | Plan | Wave | Requirement | Test Type | Automated Command | File Exists | Status |
+|---------|------|------|-------------|-----------|-------------------|-------------|--------|
+| 02-01-01 | 01 | 1 | PROV-01 | unit | `go test ./pkg/providers/... -run TestTier1` | ✅ | ⬜ pending |
+| 02-01-02 | 01 | 1 | PROV-02 | unit | `go test ./pkg/providers/... -run TestTier2` | ✅ | ⬜ pending |
+| 02-02-01 | 02 | 1 | PROV-01,PROV-02 | integration | `go test ./pkg/engine/... -run TestScan` | ✅ | ⬜ pending |
+
+*Status: ⬜ pending · ✅ green · ❌ red · ⚠️ flaky*
+
+---
+
+## Wave 0 Requirements
+
+Existing infrastructure covers all phase requirements — Phase 1 established go.mod, test framework, and testdata fixtures.
+
+---
+
+## Manual-Only Verifications
+
+| Behavior | Requirement | Why Manual | Test Instructions |
+|----------|-------------|------------|-------------------|
+| `keyhunter providers stats` shows 26 providers | PROV-01,PROV-02 | CLI output formatting | Run `go run . providers stats` and verify count shows 26+ |
+
+---
+
+## 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 < 10s
+- [ ] `nyquist_compliant: true` set in frontmatter
+
+**Approval:** pending