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/rootpool/types/types.go

@@ -0,0 +1,43 @@
+package types
+
+import "encoding/json"
+
+const (
+	ModuleName   = "rootpool"
+	StoreKey     = ModuleName
+	RouterKey    = ModuleName
+	QuerierRoute = ModuleName
+)
+
+// RootPool is the mesh's treasury (§5)
+// Attested by Watchers, visible to every Holder.
+type RootPool struct {
+	BalanceGrain    int64  `json:"balance_grain" yaml:"balance_grain"`
+	LastAttestation int64  `json:"last_attestation" yaml:"last_attestation"`
+	QuorumMet       bool   `json:"quorum_met" yaml:"quorum_met"`
+	ReserveRatioPct uint32 `json:"reserve_ratio_pct" yaml:"reserve_ratio_pct"`
+}
+
+// RootPoolEntry tracks incoming/outgoing Root-Pool movements
+type RootPoolEntry struct {
+	EntryID   string `json:"entry_id" yaml:"entry_id"`
+	Source    string `json:"source" yaml:"source"`
+	Amount    int64  `json:"amount" yaml:"amount"`
+	Reason    string `json:"reason" yaml:"reason"`
+	Timestamp int64  `json:"timestamp" yaml:"timestamp"`
+}
+
+type Params struct{}
+
+func DefaultParams() Params { return Params{} }
+
+type GenesisState struct {
+	Params   Params   `json:"params" yaml:"params"`
+	RootPool RootPool `json:"root_pool" yaml:"root_pool"`
+}
+
+func DefaultGenesisState() *GenesisState {
+	return &GenesisState{Params: DefaultParams()}
+}
+
+func ValidateGenesis(bz json.RawMessage) error { return nil }