Add Field Agents compendium: 8 pregen agents

Eight ready-to-play agents spanning the combat spectrum, each with stats,
skills, a bio, employer/education, two bonds, and appropriate firearms:
- SITKA (Special Operator, elite) ... MERCER (Forensic Scientist, support).
All are combat-capable (firearms 40-80). Registered as packs/field-agents.

Portraits: agents use a neutral placeholder token; build/gen-field-agents.mjs
auto-wires per-agent pencil portraits from assets/tokens/<name>.webp once
present (see assets/tokens/README.md for filenames). Build script committed
for reproducibility.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

system.json

@@ -108,6 +108,7 @@
                 "armor",
                 "hand-to-hand-weapons",
                 "field-equipment",
+                "field-agents",
                 "agent-pregens",
                 "operation-code-name-generator-tables"
             ],
@@ -172,6 +173,18 @@
                 "ASSISTANT": "OWNER"
             }
         },
+        {
+            "name": "field-agents",
+            "label": "Field Agents (DG2)",
+            "system": "deltagreen2",
+            "path": "packs/field-agents",
+            "type": "Actor",
+            "flags": {},
+            "ownership": {
+                "PLAYER": "OBSERVER",
+                "ASSISTANT": "OWNER"
+            }
+        },
         {
             "name": "agent-pregens",
             "label": "Agent Pregens",