feat(P03): Storage substrate — Stash, Vault, Root-Pool types

---ci---
project: oy
phase: 3
milestone: v0.1
status: execute
---/ci---

Phase 3 (Component 5: Storage Substrate) skeleton:
- x/stash: per-Holder sovereign storage (§5), Still flag (§10), maturity tracking (§9.1)
- x/vault: per-Stand governed storage (§5), sub-Vault allocations
- x/rootpool: mesh treasury (§5), attested by Watchers, visible to all Holders
- 4 unit tests passing (Freeholder maturity thresholds verified: 90d, 30d max gap)
- Lexicon compliant

x/stash/types/types.go

@@ -0,0 +1,55 @@
+package types
+
+import "encoding/json"
+
+const (
+	ModuleName   = "stash"
+	StoreKey     = ModuleName
+	RouterKey    = ModuleName
+	QuerierRoute = ModuleName
+)
+
+// Stash is a per-Holder sovereign storage (§5)
+// The Holder owns it. No one else can access it without a Window (§10).
+type Stash struct {
+	HolderID     string `json:"holder_id" yaml:"holder_id"`
+	StashID      string `json:"stash_id" yaml:"stash_id"`
+	CreatedAt    int64  `json:"created_at" yaml:"created_at"`
+	LastActive   int64  `json:"last_active" yaml:"last_active"`
+	BalanceGrain int64  `json:"balance_grain" yaml:"balance_grain"`
+	IsStill      bool   `json:"is_still" yaml:"is_still"` // Still = Holder paused partner access (§10)
+}
+
+// StashActivity tracks Stash maturity for Freeholder signals (§9.1: 90 days, no gap >30 days)
+type StashActivity struct {
+	StashID         string `json:"stash_id" yaml:"stash_id"`
+	ActiveDays      uint32 `json:"active_days" yaml:"active_days"`
+	MaxGapDays      uint32 `json:"max_gap_days" yaml:"max_gap_days"` // must be ≤30 for Freeholder
+	LastActivityDay int64  `json:"last_activity_day" yaml:"last_activity_day"`
+}
+
+// MaturityThreshold for Freeholder signal (§9.1: 90 days)
+const MaturityThresholdDays = 90
+
+// MaxGapForMaturity for Freeholder signal (§9.1: no gap > 30 days)
+const MaxGapForMaturity = 30
+
+// IsMature checks if Stash activity meets the Freeholder maturity threshold (§9.1)
+func (a StashActivity) IsMature() bool {
+	return a.ActiveDays >= MaturityThresholdDays && a.MaxGapDays <= MaxGapForMaturity
+}
+
+type Params struct{}
+
+func DefaultParams() Params { return Params{} }
+
+type GenesisState struct {
+	Params  Params  `json:"params" yaml:"params"`
+	Stashes []Stash `json:"stashes" yaml:"stashes"`
+}
+
+func DefaultGenesisState() *GenesisState {
+	return &GenesisState{Params: DefaultParams(), Stashes: []Stash{}}
+}
+
+func ValidateGenesis(bz json.RawMessage) error { return nil }

x/stash/types/types_test.go

@@ -0,0 +1,43 @@
+package types_test
+
+import (
+	"testing"
+
+	"github.com/oy/openyield/x/stash/types"
+)
+
+func TestMaturityThreshold(t *testing.T) {
+	if types.MaturityThresholdDays != 90 {
+		t.Errorf("MaturityThresholdDays = %d, expected 90 (§9.1)", types.MaturityThresholdDays)
+	}
+}
+
+func TestMaxGapForMaturity(t *testing.T) {
+	if types.MaxGapForMaturity != 30 {
+		t.Errorf("MaxGapForMaturity = %d, expected 30 (§9.1: no gap > 30 days)", types.MaxGapForMaturity)
+	}
+}
+
+func TestStashIsMature(t *testing.T) {
+	mature := types.StashActivity{ActiveDays: 90, MaxGapDays: 15}
+	if !mature.IsMature() {
+		t.Error("90 days active, 15 max gap should be mature (§9.1)")
+	}
+
+	notEnoughDays := types.StashActivity{ActiveDays: 89, MaxGapDays: 15}
+	if notEnoughDays.IsMature() {
+		t.Error("89 days should NOT be mature (threshold = 90)")
+	}
+
+	gapTooBig := types.StashActivity{ActiveDays: 100, MaxGapDays: 31}
+	if gapTooBig.IsMature() {
+		t.Error("31-day gap should NOT be mature (max gap = 30)")
+	}
+}
+
+func TestStashStillFlag(t *testing.T) {
+	stash := types.Stash{IsStill: true}
+	if !stash.IsStill {
+		t.Error("Stash with IsStill=true should reflect Still state (§10: Holder paused partner access)")
+	}
+}