Give item categories and subtypes real types (refactor step 2)

ObjectKind separates what an item is from how it draws: Object.Type
(a byte that doubled as the map character) becomes Kind ObjectKind,
with Glyph() producing the display character and objectKindForGlyph
converting back at the map boundary. KindWand covers the C 'stick'
category. The magic-missile bolt uses KindGold, matching C's literal
o_type='*' trick, with a comment.

PotionKind, ScrollKind, RingKind, WandKind, WeaponKind, ArmorKind and
TrapKind are now iota enums with Stringer (names come from the base
info tables); Object gains typed accessors (obj.RingKind(), ...) and
Launch is typed WeaponKind. beTrapped returns TrapKind. The
getItem/inventory/whatis prompt filters take ObjectKind, with
KindCallable/KindRingOrStick replacing the C CALLABLE/R_OR_S
sentinels; wizard.c's type_name table is subsumed by
ObjectKind.String(). IsRing/IsWearing/initWeapon/doPot signatures are
typed accordingly.

The save format version becomes 5.4.4-go2: the gob field rename would
otherwise silently zero Kind when reading old saves.

No behavior change; full suite green.

game/effects_test.go

@@ -22,8 +22,8 @@ func give(g *RogueGame, obj *Object) byte {
 func TestQuaffHealingPotion(t *testing.T) {
 	g := mkGameInput(t, 5, "")
 	pot := newObject()
-	pot.Type = Potion
-	pot.Which = PotionHealing
+	pot.Kind = KindPotion
+	pot.Which = int(PotionHealing)
 	ch := give(g, pot)
 	g.scr.term.(*testTerm).input = []byte{ch}
 
@@ -43,8 +43,8 @@ func TestQuaffHealingPotion(t *testing.T) {
 func TestQuaffConfusionSetsFlagAndFuse(t *testing.T) {
 	g := mkGameInput(t, 5, "")
 	pot := newObject()
-	pot.Type = Potion
-	pot.Which = PotionConfusion
+	pot.Kind = KindPotion
+	pot.Which = int(PotionConfusion)
 	ch := give(g, pot)
 	g.scr.term.(*testTerm).input = []byte{ch}
 
@@ -67,8 +67,8 @@ func TestQuaffConfusionSetsFlagAndFuse(t *testing.T) {
 func TestReadEnchantArmor(t *testing.T) {
 	g := mkGameInput(t, 5, "")
 	scr := newObject()
-	scr.Type = Scroll
-	scr.Which = ScrollEnchantArmor
+	scr.Kind = KindScroll
+	scr.Which = int(ScrollEnchantArmor)
 	ch := give(g, scr)
 	g.scr.term.(*testTerm).input = []byte{ch}
 
@@ -90,8 +90,8 @@ func TestReadHoldMonsterFreezesAdjacent(t *testing.T) {
 	tp := spawnAdjacent(g, 'Z')
 	tp.Flags.Set(Awake)
 	scr := newObject()
-	scr.Type = Scroll
-	scr.Which = ScrollHoldMonster
+	scr.Kind = KindScroll
+	scr.Which = int(ScrollHoldMonster)
 	ch := give(g, scr)
 	g.scr.term.(*testTerm).input = []byte{ch}
 
@@ -111,8 +111,8 @@ func TestHoldScrollGreedyMonsterQuirk(t *testing.T) {
 	tp := spawnAdjacent(g, 'O')
 	tp.Flags.Set(Awake)
 	scr := newObject()
-	scr.Type = Scroll
-	scr.Which = ScrollHoldMonster
+	scr.Kind = KindScroll
+	scr.Which = int(ScrollHoldMonster)
 	ch := give(g, scr)
 	g.scr.term.(*testTerm).input = []byte{ch}
 
@@ -132,8 +132,8 @@ func TestZapSlowMonster(t *testing.T) {
 	g := mkGameInput(t, 5, "")
 	tp := spawnAdjacent(g, 'Z')
 	stick := newObject()
-	stick.Type = Stick
-	stick.Which = WandSlowMonster
+	stick.Kind = KindWand
+	stick.Which = int(WandSlowMonster)
 	g.fixStick(stick)
 	ch := give(g, stick)
 	g.scr.term.(*testTerm).input = []byte{ch}