feat(client): ContentDB loads /content + mirrors the api id-resolution check

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

client/tests/unit/test_content_db.gd

@@ -0,0 +1,52 @@
+extends "res://addons/gut/test.gd"
+
+const ContentDB = preload("res://scripts/content/content_db.gd")
+
+var db
+
+
+func before_each():
+	db = ContentDB.new()
+	db.load_from(ContentDB.default_content_root())
+
+
+func _deserter() -> Dictionary:
+	return ContentDB.load_json(ContentDB.origin_path("deserter"))
+
+
+func test_loads_world_ids():
+	assert_true(db.has_location("greywater_docks"))
+	assert_true(db.has_quest("find_the_ledger"))
+	assert_true(db.has_item("worn_shortsword"))
+	assert_true(db.has_item("coin"))
+
+
+func test_companions_are_brannoc_and_cadwyn():
+	var ids := []
+	for n in db.companions():
+		ids.append(n["id"])
+	ids.sort()
+	assert_eq(ids, ["brannoc_thane","cadwyn_vell"])
+
+
+func test_good_origin_has_no_unresolved_refs():
+	assert_eq(db.unresolved_refs(_deserter()), [])
+
+
+func test_broken_location_ref_detected():
+	var o := _deserter()
+	o["start_location_id"] = "nowhere"
+	assert_true("location:nowhere" in db.unresolved_refs(o))
+
+
+func test_broken_item_ref_detected():
+	var o := _deserter()
+	o["inventory_grants"] = o["inventory_grants"].duplicate(true)
+	o["inventory_grants"].append({"item_id": "ghost_blade", "qty": 1})
+	assert_true("item:ghost_blade" in db.unresolved_refs(o))
+
+
+func test_null_quest_ref_resolves():
+	var o := _deserter()
+	o["start_quest_id"] = null
+	assert_eq(db.unresolved_refs(o), [])