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.

backend/app/reader/queries.py

@@ -44,9 +44,11 @@ def video(db: Session, video_id: str) -> Video | None:
 def tags_with_counts(db: Session, user: User) -> list[tuple[Tag, int, int]]:
     """The tags this user sees (the shared system ones and their own), by category then name, each
     with how many channel links it has and how many of the user's own links sit on a channel they
-    subscribe to — the rows the Channels page's tag filter shows. A link outlives an unsubscribe,
-    so the two differ."""
-    subscribed = select(Subscription.channel_id).where(owned_by(Subscription.user_id, user))
+    subscribe to and have not hidden — the rows the Channels page's tag filter shows (a hidden
+    channel has its own tab). A link outlives an unsubscribe and a hide, so the two differ."""
+    subscribed = select(Subscription.channel_id).where(
+        owned_by(Subscription.user_id, user), Subscription.hidden.is_(False)
+    )
     on_subscribed = dict(
         db.execute(
             select(ChannelTag.tag_id, func.count(ChannelTag.id))