Implemented Active Effects.

Used AE to implement exhaustion, stimulants, and rest.

module/data/active-effect/dg-active-effect-data.js

@@ -0,0 +1,55 @@
+const { ArrayField, SchemaField, StringField, NumberField, AnyField } =
+  foundry.data.fields;
+
+/**
+ * Delta Green Active Effect system data — matches core change schema with `final` as the default phase.
+ * @extends {foundry.data.ActiveEffectTypeDataModel}
+ */
+export default class DGActiveEffectTypeDataModel extends foundry.data
+  .ActiveEffectTypeDataModel {
+  /** @override */
+  static defineSchema() {
+    return {
+      changes: new ArrayField(
+        new SchemaField({
+          key: new StringField({ required: true }),
+          type: new StringField({
+            required: true,
+            blank: false,
+            initial: "add",
+            validate: DGActiveEffectTypeDataModel.#validateType,
+          }),
+          value: new AnyField({
+            required: true,
+            nullable: true,
+            serializable: true,
+            initial: "",
+          }),
+          phase: new StringField({
+            required: true,
+            blank: false,
+            initial: "final",
+          }),
+          priority: new NumberField(),
+        }),
+      ),
+    };
+  }
+
+  /**
+   * @param {string} type
+   * @returns {true}
+   */
+  static #validateType(type) {
+    if (type.length < 3) throw new Error("must be at least three characters long");
+    if (
+      !/^custom\.-?\d+$/.test(type) &&
+      !type.split(".").every((s) => /^[a-z0-9]+$/i.test(s))
+    ) {
+      throw new Error(
+        'A change type must either be a sequence of dot-delimited, alpha-numeric substrings or of the form "custom.{number}"',
+      );
+    }
+    return true;
+  }
+}