fix: share, upload, crop, auto-skip, tag chips and See all hold what they claim

- Share: a link that expired is never copied (the dialog and one-click Share pick a live one,
  else make one), says it expired, and the copy-on-open claim clears on the next copy.
- A password-protected file link asks to open a file, not to watch a video.
- Upload: Cancel, the close button or the backdrop while naming a folder makes no folder; a failed
  refetch keeps the target; a folder being made says so.
- Crop: an infinite number is dropped, not a 500; an unprobed clip's size follows a shown-size crop;
  the edit_spec docs name frame_w/frame_h; the join and rotated paths are tested.
- Auto-skip: the wait gives way on a marker too short for it, so the skip still fires.
- Tag chips count the followed channels (subscribed_count) and a toggled chip keeps the focus.
- Continue watching's See all sorts by last watched when in progress was already on.

frontend/src/lib/api/tags.ts

@@ -7,7 +7,11 @@ export interface Tag {
   color: string | null;
   category: string;
   system: boolean;
+  /** 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. */
+  subscribed_count: number;
 }
 
 // One suggested user-tag for a channel, learned from the user's own manual-tag pattern.