fix: tag counts, chip focus, upload naming, share links and unsized clips hold after round 2

- A tag counts the followed channels the Subscriptions tab shows: hidden ones are left out, and a
  subscribe, unsubscribe, hide or tag toggle refreshes the count. The Tag manager's row and its
  hover list count the same channels as the chip; /api/tags sends both counts under their names.
- A chip's count keeps the chip's colour after a dot (a dimmed count fell under 4.5:1). A pick in
  the open "+N" fold closes it; a chip that leaves the list hands the focus to the one in its place.
  The fold is a dialog of toggle buttons, not an empty menu.
- Upload: a folder name left by a press is made once the press is over, if the dialog is still
  open, instead of guessing a dismissal from Modal's markup. While the folder is made, its place
  holds the focus and a live region says so.
- Share: an expired link has no Copy and a warn badge; the link made on open goes into the cached
  list, so a reopen makes no second one; the New link form survives the link made on open.
- Watch: a repeated Enter sends one unlock while one is on its way. See all buttons are named with
  their rail.
- An unsized clip of a rotated file gets the upright size its crop cut.

frontend/src/lib/api/tags.ts

@@ -10,7 +10,8 @@ export interface Tag {
   /** Every channel link it has, a channel the user no longer follows included (an unsubscribe keeps
    *  the link) — what deleting the tag removes. */
   channel_count: number;
-  /** The user's own links on channels they follow: the rows the Channels page's filter shows. */
+  /** The user's own links on channels they follow and have not hidden: the rows the Channels page's
+   *  filter shows (a hidden channel has its own tab). */
   subscribed_count: number;
 }