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>

package.json

@@ -16,11 +16,12 @@
     "test": "vitest run",
     "test:watch": "vitest",
     "test:coverage": "vitest run --coverage",
-    "typecheck": "tsc --noEmit",
+    "typecheck": "tsc --noEmit && npm run typecheck:client",
+    "typecheck:client": "tsc -p src/scripts/client/tsconfig.json --noEmit",
     "prepare": "husky && npm run build:client"
   },
   "lint-staged": {
-    "*.{ts,js}": [
+    "*.{ts,tsx,js,jsx}": [
       "eslint --fix",
       "prettier --write"
     ],