fix(auto-update-checker): use OpenCode cache paths for updates

Align version lookup, invalidation, and bun install with OpenCode's cache directory so updates target the loaded plugin location. Keep dependency declarations intact during invalidation so auto-update can reinstall instead of converging to uninstall.

src/hooks/auto-update-checker/constants.ts

@@ -1,19 +1,13 @@
 import * as path from "node:path"
 import * as os from "node:os"
-import { getOpenCodeConfigDir } from "../../shared"
+import { getOpenCodeCacheDir } from "../../shared/data-path"
+import { getOpenCodeConfigDir } from "../../shared/opencode-config-dir"
 
 export const PACKAGE_NAME = "oh-my-opencode"
 export const NPM_REGISTRY_URL = `https://registry.npmjs.org/-/package/${PACKAGE_NAME}/dist-tags`
 export const NPM_FETCH_TIMEOUT = 5000
 
-function getCacheDir(): string {
-  if (process.platform === "win32") {
-    return path.join(process.env.LOCALAPPDATA ?? os.homedir(), "opencode")
-  }
-  return path.join(os.homedir(), ".cache", "opencode")
-}
-
-export const CACHE_DIR = getCacheDir()
+export const CACHE_DIR = getOpenCodeCacheDir()
 export const VERSION_FILE = path.join(CACHE_DIR, "version")
 
 export function getWindowsAppdataDir(): string | null {
@@ -26,7 +20,7 @@ export const USER_OPENCODE_CONFIG = path.join(USER_CONFIG_DIR, "opencode.json")
 export const USER_OPENCODE_CONFIG_JSONC = path.join(USER_CONFIG_DIR, "opencode.jsonc")
 
 export const INSTALLED_PACKAGE_JSON = path.join(
-  USER_CONFIG_DIR,
+  CACHE_DIR,
   "node_modules",
   PACKAGE_NAME,
   "package.json"