N4/E1: T4 Estate vault — 10-slot protected item storage

The Tier-4 "Established" home now unlocks a vault: `!adventure vault
[store|take] <item>` moves items in and out of a 10-slot pool that shelters
them from `!sell all`, crafting, and combat consumption. It is also E2
gifting's prerequisite plumbing.

Implemented as a single `in_vault` flag on adventure_inventory rather than a
parallel table: a stowed item keeps its identity (id, temper, everything) and
loadAdvInventory filters it out, so a vaulted item drops out of every play
surface with one flag change and comes back untouched. DEFAULT 0 = "in play",
correct for every pre-existing row, so no bootstrap backfill.

Golden byte-identical; go test ./... green.

Claude-Session: https://claude.ai/code/session_017mEwUmmS7aQTP2NQXj6rUa

internal/plugin/adventure_vault.go

@@ -0,0 +1,125 @@
+package plugin
+
+import (
+	"fmt"
+	"strings"
+
+	"maunium.net/go/mautrix/id"
+)
+
+// N4/E1 — the Tier-4 "Established" home unlocks a vault: a fixed pool of slots
+// that shelters items from `!sell all`, crafting, and combat consumption. It is
+// pure storage — a vaulted item drops out of every play surface (loadAdvInventory
+// filters it) until it is taken back — and the plumbing E2 gifting builds on.
+const (
+	vaultCapacity     = 10 // slots an Established home provides
+	vaultMinHouseTier = 4  // Tier 4 "Established" gates the vault
+)
+
+// vaultUnlocked reports whether the character's house tier grants a vault, and a
+// player-facing refusal line when it does not.
+func vaultUnlocked(char *AdventureCharacter) (bool, string) {
+	if char.HouseTier >= vaultMinHouseTier {
+		return true, ""
+	}
+	return false, "🔒 A vault comes with an **Established** home (Tier 4). Upgrade your house at `!thom` to unlock " +
+		fmt.Sprintf("%d slots of protected storage — vaulted items are safe from `!sell all` and never spent in combat.", vaultCapacity)
+}
+
+// handleVaultCmd routes `!adventure vault [store|take] <item>`. The reply-building
+// core is client-free (renderVault / vaultStoreItem / vaultTakeItem) so it is
+// unit-testable without a Matrix stub; the handler only loads the character and
+// sends the result.
+func (p *AdventurePlugin) handleVaultCmd(ctx MessageContext, args string) error {
+	char, _, err := p.ensureCharacter(ctx.Sender)
+	if err != nil {
+		return p.SendReply(ctx.RoomID, ctx.EventID, "Failed to load your character. Try `!adventure` to create one first.")
+	}
+	if !char.Alive {
+		return p.SendDM(ctx.Sender, "You're dead. The vault stays locked.")
+	}
+	if ok, refusal := vaultUnlocked(char); !ok {
+		return p.SendDM(ctx.Sender, refusal)
+	}
+
+	lower := strings.ToLower(strings.TrimSpace(args))
+	var reply string
+	switch {
+	case lower == "" || lower == "list":
+		reply = renderVault(ctx.Sender)
+	case strings.HasPrefix(lower, "store "):
+		reply = vaultStoreItem(ctx.Sender, strings.TrimSpace(args[len("store "):]))
+	case strings.HasPrefix(lower, "take "):
+		reply = vaultTakeItem(ctx.Sender, strings.TrimSpace(args[len("take "):]))
+	default:
+		reply = "Usage: `!adventure vault` to view · `!adventure vault store <item>` · `!adventure vault take <item>`."
+	}
+	return p.SendDM(ctx.Sender, reply)
+}
+
+// renderVault shows what is stowed and how many slots remain.
+func renderVault(userID id.UserID) string {
+	items, err := loadAdvVault(userID)
+	if err != nil {
+		return "The vault door won't budge. Try again in a moment."
+	}
+	var sb strings.Builder
+	sb.WriteString(fmt.Sprintf("🏛️ **Your Vault** — %d / %d slots\n\n", len(items), vaultCapacity))
+	if len(items) == 0 {
+		sb.WriteString("Empty. `!adventure vault store <item>` to shelter something from sale or use.")
+		return sb.String()
+	}
+	for _, it := range items {
+		name := it.Name
+		if it.Temper > 0 {
+			name = fmt.Sprintf("%s +%d", name, it.Temper)
+		}
+		sb.WriteString(fmt.Sprintf("• %s — €%d\n", name, it.Value))
+	}
+	sb.WriteString("\n`!adventure vault take <item>` to bring one back into play.")
+	return sb.String()
+}
+
+// vaultStoreItem moves one matching inventory item into the vault. Guards the
+// capacity and reports the fresh slot count so the player never has to re-list.
+func vaultStoreItem(userID id.UserID, query string) string {
+	if query == "" {
+		return "Store what? `!adventure vault store <item>`."
+	}
+	if advVaultCount(userID) >= vaultCapacity {
+		return fmt.Sprintf("The vault is full (%d / %d). Take something out first with `!adventure vault take <item>`.", vaultCapacity, vaultCapacity)
+	}
+	items, err := loadAdvInventory(userID)
+	if err != nil {
+		return "Couldn't reach your inventory. Try again in a moment."
+	}
+	match := findInventoryMatch(items, query)
+	if match == nil {
+		return fmt.Sprintf("No inventory item matches %q. Check `!adventure inventory`.", query)
+	}
+	moved, err := setItemVaulted(userID, match.ID, true)
+	if err != nil || !moved {
+		return "Couldn't stow that item. Try again in a moment."
+	}
+	return fmt.Sprintf("🏛️ Stowed **%s** in the vault. %d / %d slots used.", match.Name, advVaultCount(userID), vaultCapacity)
+}
+
+// vaultTakeItem returns one matching vaulted item to the active inventory.
+func vaultTakeItem(userID id.UserID, query string) string {
+	if query == "" {
+		return "Take what? `!adventure vault take <item>`."
+	}
+	items, err := loadAdvVault(userID)
+	if err != nil {
+		return "The vault door won't budge. Try again in a moment."
+	}
+	match := findInventoryMatch(items, query)
+	if match == nil {
+		return fmt.Sprintf("Nothing in the vault matches %q. Check `!adventure vault`.", query)
+	}
+	moved, err := setItemVaulted(userID, match.ID, false)
+	if err != nil || !moved {
+		return "Couldn't retrieve that item. Try again in a moment."
+	}
+	return fmt.Sprintf("Took **%s** out of the vault and back into your pack. %d / %d slots used.", match.Name, advVaultCount(userID), vaultCapacity)
+}