refactor(migration): extract agent and hook maps (#1561)

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-opencode)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

src/shared/migration/hook-names.ts

@@ -0,0 +1,36 @@
+// Migration map: old hook names → new hook names (for backward compatibility)
+// null means the hook was removed and should be filtered out from disabled_hooks
+export const HOOK_NAME_MAP: Record<string, string | null> = {
+  // Legacy names (backward compatibility)
+  "anthropic-auto-compact": "anthropic-context-window-limit-recovery",
+  "sisyphus-orchestrator": "atlas",
+
+  // Removed hooks (v3.0.0) - will be filtered out and user warned
+  "empty-message-sanitizer": null,
+}
+
+export function migrateHookNames(
+  hooks: string[]
+): { migrated: string[]; changed: boolean; removed: string[] } {
+  const migrated: string[] = []
+  const removed: string[] = []
+  let changed = false
+
+  for (const hook of hooks) {
+    const mapping = HOOK_NAME_MAP[hook]
+
+    if (mapping === null) {
+      removed.push(hook)
+      changed = true
+      continue
+    }
+
+    const newHook = mapping ?? hook
+    if (newHook !== hook) {
+      changed = true
+    }
+    migrated.push(newHook)
+  }
+
+  return { migrated, changed, removed }
+}