refactor(hooks): remove beast-mode system integration

Remove the beast-mode-system hook and all transform wiring so Copilot-specific prompt injection is fully eliminated from the runtime pipeline.

src/config/schema.test.ts

@@ -7,6 +7,7 @@ import {
   CategoryConfigSchema,
   ExperimentalConfigSchema,
   GitMasterConfigSchema,
+  HookNameSchema,
   OhMyOpenCodeConfigSchema,
 } from "./schema"
 
@@ -393,6 +394,19 @@ describe("BuiltinCategoryNameSchema", () => {
   })
 })
 
+describe("HookNameSchema", () => {
+  test("rejects removed beast-mode-system hook name", () => {
+    //#given
+    const input = "beast-mode-system"
+
+    //#when
+    const result = HookNameSchema.safeParse(input)
+
+    //#then
+    expect(result.success).toBe(false)
+  })
+})
+
 describe("Sisyphus-Junior agent override", () => {
   test("schema accepts agents['Sisyphus-Junior'] and retains the key after parsing", () => {
     // given

src/config/schema/hooks.ts

@@ -25,7 +25,6 @@ export const HookNameSchema = z.enum([
   "interactive-bash-session",
 
   "thinking-block-validator",
-  "beast-mode-system",
   "ralph-loop",
   "category-skill-reminder",