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/citation.ts

@@ -1,4 +1,5 @@
 import {getCurrentLocale} from '../utils.ts';
+import {errorMessage} from '../modules/errors.ts';
 import {fomanticQuery} from '../modules/fomantic/base.ts';
 import {localUserSettings} from '../modules/user-settings.ts';
 
@@ -46,7 +47,7 @@ export async function initCitationFileCopyContent() {
     try {
       await initInputCitationValue(citationCopyApa, citationCopyBibtex);
     } catch (e) {
-      console.error(`initCitationFileCopyContent error: ${e}`, e);
+      console.error(`initCitationFileCopyContent error: ${errorMessage(e)}`, e);
       return;
     }
     updateUi();