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/types.go

@@ -62,12 +62,6 @@ const (
 	Stick    byte = '/'
 )
 
-// Pseudo-types for item-selection prompts (rogue.h)
-const (
-	Callable = -1
-	RorS     = -2
-)
-
 // Various constants (rogue.h)
 const (
 	HealTime    = 30
@@ -173,22 +167,37 @@ func (f PlaceFlags) Has(b PlaceFlags) bool { return f&b != 0 }
 func (f *PlaceFlags) Set(b PlaceFlags)     { *f |= b }
 func (f *PlaceFlags) Clear(b PlaceFlags)   { *f &^= b }
 
-// Trap types (rogue.h)
+// TrapKind identifies a trap (rogue.h trap types). The kind is stored in
+// the low bits of a map cell's PlaceFlags (FTrapMask).
+type TrapKind int
+
 const (
-	TrapDoor     = 0
-	TrapArrow    = 1
-	TrapSleep    = 2
-	TrapBear     = 3
-	TrapTeleport = 4
-	TrapDart     = 5
-	TrapRust     = 6
-	TrapMystery  = 7
-	NumTrapTypes = 8
+	TrapDoor     TrapKind = 0
+	TrapArrow    TrapKind = 1
+	TrapSleep    TrapKind = 2
+	TrapBear     TrapKind = 3
+	TrapTeleport TrapKind = 4
+	TrapDart     TrapKind = 5
+	TrapRust     TrapKind = 6
+	TrapMystery  TrapKind = 7
+	NumTrapTypes          = 8
 )
 
-// Potion types (rogue.h)
+// String returns the trap's display name, article included, as the C
+// tr_name table had it.
+func (t TrapKind) String() string {
+	if t < 0 || t >= NumTrapTypes {
+		return "a bizarre trap"
+	}
+	return trName[t]
+}
+
+// PotionKind identifies a potion (rogue.h potion types).
+type PotionKind int
+
+// Potion kinds (rogue.h)
 const (
-	PotionConfusion = iota
+	PotionConfusion PotionKind = iota
 	PotionLSD
 	PotionPoison
 	PotionGainStrength
@@ -205,9 +214,20 @@ const (
 	NumPotionTypes
 )
 
-// Scroll types (rogue.h)
+// String returns the potion's true name ("healing", "haste self", ...).
+func (p PotionKind) String() string {
+	if p < 0 || p >= NumPotionTypes {
+		return "strange potion"
+	}
+	return basePotInfo[p].Name
+}
+
+// ScrollKind identifies a scroll (rogue.h scroll types).
+type ScrollKind int
+
+// Scroll kinds (rogue.h)
 const (
-	ScrollMonsterConfusion = iota
+	ScrollMonsterConfusion ScrollKind = iota
 	ScrollMagicMapping
 	ScrollHoldMonster
 	ScrollSleep
@@ -228,9 +248,20 @@ const (
 	NumScrollTypes
 )
 
-// Weapon types (rogue.h)
+// String returns the scroll's true name ("magic mapping", ...).
+func (s ScrollKind) String() string {
+	if s < 0 || s >= NumScrollTypes {
+		return "strange scroll"
+	}
+	return baseScrInfo[s].Name
+}
+
+// WeaponKind identifies a weapon (rogue.h weapon types).
+type WeaponKind int
+
+// Weapon kinds (rogue.h)
 const (
-	WeaponMace = iota
+	WeaponMace WeaponKind = iota
 	WeaponLongSword
 	WeaponBow
 	WeaponArrow
@@ -243,9 +274,20 @@ const (
 	NumWeaponTypes = WeaponFlame
 )
 
-// Armor types (rogue.h)
+// String returns the weapon's name ("mace", "two handed sword", ...).
+func (w WeaponKind) String() string {
+	if w < 0 || w > WeaponFlame {
+		return "strange weapon"
+	}
+	return baseWeapInfo[w].Name
+}
+
+// ArmorKind identifies a suit of armor (rogue.h armor types).
+type ArmorKind int
+
+// Armor kinds (rogue.h)
 const (
-	ArmorLeather = iota
+	ArmorLeather ArmorKind = iota
 	ArmorRingMail
 	ArmorStuddedLeather
 	ArmorScaleMail
@@ -256,9 +298,20 @@ const (
 	NumArmorTypes
 )
 
-// Ring types (rogue.h)
+// String returns the armor's name ("ring mail", "plate mail", ...).
+func (a ArmorKind) String() string {
+	if a < 0 || a >= NumArmorTypes {
+		return "strange armor"
+	}
+	return baseArmInfo[a].Name
+}
+
+// RingKind identifies a ring (rogue.h ring types).
+type RingKind int
+
+// Ring kinds (rogue.h)
 const (
-	RingProtection = iota
+	RingProtection RingKind = iota
 	RingAddStrength
 	RingSustainStrength
 	RingSearching
@@ -275,9 +328,20 @@ const (
 	NumRingTypes
 )
 
-// Rod/Wand/Staff types (rogue.h)
+// String returns the ring's true name ("add strength", "stealth", ...).
+func (r RingKind) String() string {
+	if r < 0 || r >= NumRingTypes {
+		return "strange ring"
+	}
+	return baseRingInfo[r].Name
+}
+
+// WandKind identifies a wand or staff (rogue.h rod/wand/staff types).
+type WandKind int
+
+// Wand kinds (rogue.h)
 const (
-	WandLight = iota
+	WandLight WandKind = iota
 	WandInvisibility
 	WandLightning
 	WandFire
@@ -294,6 +358,14 @@ const (
 	NumWandTypes
 )
 
+// String returns the wand/staff's true name ("lightning", ...).
+func (w WandKind) String() string {
+	if w < 0 || w >= NumWandTypes {
+		return "strange stick"
+	}
+	return baseWsInfo[w].Name
+}
+
 // Coord is a position on the level (rogue.h coord). A value type: the C
 // ce(a,b) macro is plain == here.
 type Coord struct {
@@ -349,9 +421,6 @@ type Stone struct {
 // CTRL maps a letter to its control character, as the C CTRL() macro.
 func CTRL(c byte) byte { return c & 0o37 }
 
-// IsMult reports whether an object type stacks in the pack (rogue.h ISMULT).
-func IsMult(typ byte) bool { return typ == Potion || typ == Scroll || typ == Food }
-
 // distance returns the squared distance between two points (chase.c dist).
 func distance(y1, x1, y2, x2 int) int {
 	dx := x2 - x1