Enable strict TypeScript, add errorMessage helper (#37292)

Enable full TypeScript `strict` mode and fix issues discovered during
this refactor. Introduced a `errorMessage` helper function to cleanly
extract a error messages from the `unknown` type.

Signed-off-by: silverwind <me@silverwind.io>
Co-authored-by: Claude (claude-opus-4-7) <noreply@anthropic.com>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

web_src/js/features/common-fetch-action.ts

@@ -1,6 +1,7 @@
 import {GET, request} from '../modules/fetch.ts';
 import {hideToastsAll, showErrorToast} from '../modules/toast.ts';
 import {addDelegatedEventListener, createElementFromHTML} from '../utils/dom.ts';
+import {errorMessage} from '../modules/errors.ts';
 import {confirmModal, createConfirmModal} from './comp/ConfirmModal.ts';
 import {ignoreAreYouSure} from '../vendor/jquery.are-you-sure.ts';
 import {registerGlobalSelectorFunc} from '../modules/observer.ts';
@@ -134,10 +135,10 @@ async function performActionRequest(el: HTMLElement, opt: FetchActionOpts) {
       return;
     }
     await handleFetchActionError(resp);
-  } catch (e) {
-    if (e.name !== 'AbortError') {
-      console.error(`Fetch action request error:`, e);
-      showErrorToast(`Error: ${e.message ?? e}`);
+  } catch (err) {
+    if ((err as Error).name !== 'AbortError') {
+      console.error(`Fetch action request error:`, err);
+      showErrorToast(`Error: ${errorMessage(err)}`);
     }
   } finally {
     toggleLoadingIndicator(el, opt, false);