feat(rules): add alignment field to Combatant with axis gating flags

Adds the PF1e two-axis alignment code (LG/NG/CG/LN/N/CN/LE/NE/CE,
default N) to the Combatant model with a strict validator, derived
is_lawful/is_chaotic/is_good/is_evil properties, exposure in the
observation snapshot, and alignment values for all monsters and PCs
sourced from the bestiary KB and the Foundry sheets.

data/pcs/esha_mount.json

@@ -1,5 +1,6 @@
 {
   "name": "Esha's Mount",
+  "alignment": "N",
   "level": 4,
   "size": "Large",
   "abilities": {
@@ -44,7 +45,7 @@
       "natural": true
     }
   ],
-  "notes": "Light-horse mount shared with Esha's sheet: hooves are 1d4 bludgeoning (SRD Bestiary horse, light - 2 hooves 1d4), natural attacks. No bite encoded: the SRD light horse has no bite attack and the Foundry sheet lists no mount bite (unlike Jeanne's sheet, which does).",
+  "notes": "Light-horse mount shared with Esha's sheet: hooves are 1d4 bludgeoning (SRD Bestiary horse, light - 2 hooves 1d4), natural attacks. No bite encoded: the SRD light horse has no bite attack and the Foundry sheet lists no mount bite (unlike Jeanne's sheet, which does). Alignment inferred: SRD animal (horse) is typically neutral; no alignment on the sheet",
   "source": "fiches_personnages/esha_sheet.json (mount)",
   "features": [
     "Combat Reflexes",