fix(test): move auto-slash-command-leak test to isolated subdirectory

mock.module('./executor') leaks across all files in the same batch because
Bun runs test files in a directory in parallel. The afterAll restore trick
doesn't work when other files load the module concurrently at startup.

Moving the leak test to its own subdirectory (leak/) ensures CI's batch
runner isolates it in a separate bun test invocation, preventing executor
mock contamination in executor-resolution.test.ts and index.test.ts.

src/hooks/auto-slash-command/leak/auto-slash-command-leak.test.ts

@@ -1,12 +1,12 @@
 import { afterAll, beforeEach, describe, expect, it, mock, spyOn } from "bun:test"
-import { AUTO_SLASH_COMMAND_TAG_OPEN } from "./constants"
+import { AUTO_SLASH_COMMAND_TAG_OPEN } from "../constants"
 import type {
   AutoSlashCommandHookInput,
   AutoSlashCommandHookOutput,
   CommandExecuteBeforeInput,
   CommandExecuteBeforeOutput,
-} from "./types"
-import * as shared from "../../shared"
+} from "../types"
+import * as shared from "../../../shared"
 
 const executeSlashCommandMock = mock(
   async (parsed: { command: string; args: string; raw: string }) => ({
@@ -15,7 +15,7 @@ const executeSlashCommandMock = mock(
   })
 )
 
-mock.module("./executor", () => ({
+mock.module("../executor", () => ({
   executeSlashCommand: executeSlashCommandMock,
 }))
 
@@ -23,13 +23,13 @@ afterAll(async () => {
   mock.restore()
   // Restore the real executor module so subsequent test files in the same batch
   // (e.g. executor-resolution.test.ts) don't get the mocked version
-  const realExecutor = await import("./executor")
-  mock.module("./executor", () => realExecutor)
+  const realExecutor = await import("../executor")
+  mock.module("../executor", () => realExecutor)
 })
 
 const logMock = spyOn(shared, "log").mockImplementation(() => {})
 
-const { createAutoSlashCommandHook } = await import("./hook")
+const { createAutoSlashCommandHook } = await import("../hook")
 
 function createChatInput(sessionID: string, messageID: string): AutoSlashCommandHookInput {
   return {