fix(rules): lich data conforms to the KB stat block

Verified against the KB (bestiary/lich.md, Bestiary Lich CR 12):
- bab 8 -> 5 ('Base Atk +5')
- Paralyzing Touch attack_bonus 10 -> 5 ('Melee touch +5 (1d8+5 plus
  paralyzing touch)') and marked natural: true (template: 'A lich has a
  touch attack that it can use once per round as a natural weapon [...]
  treated as a primary natural weapon' - no BAB iteratives per e5691bd)
- damage_bonus 5 -> 0: the +5 (1 point per 2 HD) is already in the
  1d8+5 formula and _resolve_swing adds damage_bonus on top (double
  counting: the old data dealt 1d8+10)
- ac 25/14/23 -> 23/14/21 ('AC 23, touch 14, flat-footed 21'; touch was
  already correct)
- saves 10/10/14 -> 6/7/11 ('Fort +6, Ref +7, Will +11')
- con_score 14 -> 10: 'Being undead, a lich has no Constitution score'
  (Con '—'); the int-only schema encodes 'no score' as the neutral 10
  (modifier +0), inert anyway since undead are destroyed at hp <= 0.
Left as intentional engine tuning (residual divergences, documented in
the final report): hp 100 vs 111, Str 12 vs 10, Int 20 vs 22,
initiative +6 vs +2, fear aura 30 ft/DC 22 vs 60 ft/DC 18.
Golden transcript untouched (the lich wins via Magic Missile before any
weapon swing; MM DC depends on Int, unchanged). Pinned a new
test_json_matches_srd_stat_block.

data/monsters/lich.json

@@ -6,24 +6,24 @@
   "abilities": {
     "str_score": 12,
     "dex_score": 14,
-    "con_score": 14,
+    "con_score": 10,
     "int_score": 20,
     "wis_score": 14,
     "cha_score": 16
   },
   "hp_max": 100,
   "ac": {
-    "total": 25,
+    "total": 23,
     "touch": 14,
-    "flat_footed": 23
+    "flat_footed": 21
   },
-  "bab": 8,
+  "bab": 5,
   "initiative_mod": 6,
   "speed_land_ft": 30,
   "saves": {
-    "fort": 10,
-    "ref": 10,
-    "will": 14
+    "fort": 6,
+    "ref": 7,
+    "will": 11
   },
   "casting_ability": "int",
   "spell_slots": {
@@ -39,14 +39,15 @@
       "id": "lich:touch",
       "name": "Paralyzing Touch",
       "kind": "touch",
-      "attack_bonus": 10,
+      "attack_bonus": 5,
+      "natural": true,
       "damage": [
         {
           "formula": "1d8+5",
           "types": ["negative"]
         }
       ],
-      "damage_bonus": 5,
+      "damage_bonus": 0,
       "crit_range": 20,
       "crit_mult": 2,
       "reach_ft": 5,