fix(claude-code-hooks): cache idle hook config and parent lookups

Reduce repeated session.idle work by reusing hook config loads across a short TTL and by retrying parent session lookup instead of permanently caching transient failures.

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

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

src/hooks/claude-code-hooks/handlers/session-event-handler-retry.test.ts

@@ -0,0 +1,67 @@
+const { beforeEach, describe, expect, mock, test } = require("bun:test")
+
+const executeStopHooks = mock(async (context: { parentSessionId?: string }) => ({
+  block: false,
+  observedParentSessionId: context.parentSessionId,
+}))
+
+mock.module("../config", () => ({
+  clearClaudeHooksConfigCache: () => {},
+  loadClaudeHooksConfig: async () => null,
+}))
+
+mock.module("../config-loader", () => ({
+  clearPluginExtendedConfigCache: () => {},
+  loadPluginExtendedConfig: async () => ({}),
+}))
+
+mock.module("../stop", () => ({
+  executeStopHooks,
+}))
+
+const { createSessionEventHandler } = await import("./session-event-handler")
+
+describe("createSessionEventHandler retry behavior", () => {
+  beforeEach(() => {
+    executeStopHooks.mockClear()
+  })
+
+  test("#given transient parent lookup failure #when the next idle succeeds #then stop hooks receive the later parent session id", async () => {
+    //#given
+    let getCallCount = 0
+    const handler = createSessionEventHandler(
+      {
+        directory: "/repo",
+        client: {
+          session: {
+            get: async () => {
+              getCallCount += 1
+              if (getCallCount === 1) {
+                throw new Error("temporary failure")
+              }
+              return { data: { parentID: "ses_parent" } }
+            },
+            prompt: async () => undefined,
+          },
+        },
+      } as never,
+      {},
+    )
+
+    //#when
+    await handler({ event: { type: "session.idle", properties: { sessionID: "ses_retry" } } })
+    await handler({ event: { type: "session.idle", properties: { sessionID: "ses_retry" } } })
+
+    //#then
+    expect(getCallCount).toBe(2)
+    expect(executeStopHooks).toHaveBeenLastCalledWith(
+      expect.objectContaining({
+        parentSessionId: "ses_parent",
+      }),
+      null,
+      {},
+    )
+  })
+})
+
+export {}