chore(ai): remove dead code (agent)

Removed unused exports and functions identified as dead code.
- Removed unused exports from `js/utils/storage.js`, `js/utils/storagePointer.js`, `js/utils/videoTags.js`, `js/ui/moderationCopy.js`.
- Removed unused function `updateTagPillStrip` from `js/ui/components/tagPillList.js` and associated tests.
- Updated `tests/utils/video-tags.test.mjs` to remove test for private function.
- Added `artifacts/depcheck.json` showing dependency analysis.

Co-authored-by: PR0M3TH3AN <[email protected]>

js/utils/storagePointer.js

@@ -8,7 +8,7 @@ export function normalizeStoragePointer(value) {
   return safeTrim(value);
 }
 
-export function parseStoragePointer(value) {
+function parseStoragePointer(value) {
   const normalized = normalizeStoragePointer(value);
   if (!normalized) {
     return null;
@@ -38,7 +38,7 @@ export function buildStoragePointerValue({ provider, prefix } = {}) {
   return `${normalizedProvider}:${normalizedPrefix}`;
 }
 
-export function deriveStoragePrefixFromUrl(url) {
+function deriveStoragePrefixFromUrl(url) {
   const trimmed = safeTrim(url);
   if (!trimmed || !/^https?:\/\//i.test(trimmed)) {
     return "";