fix(lint): close type-check gaps in client scripts and tooling

Remove unused import flagged by CI lint, then harden the toolchain so
such issues are caught before push:

- lint-staged now also matches .tsx/.jsx (previously .tsx files skipped
  the pre-commit eslint pass, which is how the error reached CI)
- eslint ignores generated client bundles (gitignored, not worth linting)
- typecheck now also runs the client tsconfig; the hand-written browser
  source was excluded from the root config and never type-checked
- consolidate the window global augmentations (showToast,
  parseJsonResponseOrThrow) into a single client globals.d.ts; the inline
  declare-global blocks failed (non-module files) and masked real errors

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/scripts/client/dashboard.ts

@@ -341,21 +341,6 @@ function refreshFeedRowCache(): void {
   updateFeedSelectionState();
 }
 
-interface ToastHandle {
-  update?: (msg: string, opts?: Record<string, unknown>) => void;
-  dismiss?: () => void;
-}
-
-declare global {
-  interface Window {
-    showToast?: (msg: string, opts?: Record<string, unknown>) => ToastHandle;
-    parseJsonResponseOrThrow?: (
-      res: Response,
-      opts?: Record<string, unknown>,
-    ) => Promise<Record<string, unknown>>;
-  }
-}
-
 function setupFeedDeleteButtons(): void {
   const buttons = Array.from(
     document.querySelectorAll<HTMLButtonElement>(