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.

backend/tests/test_reader_service.py

@@ -14,7 +14,7 @@ from sqlalchemy import select
 from sqlalchemy.exc import IntegrityError
 
 from app.discover import pins
-from app.catalog.models import Channel, Video
+from app.catalog.models import Channel, Subscription, Video
 from app.reader import queries, service
 from app.reader.models import ChannelTag, ComfortPin, Playlist, PlaylistItem, Tag, VideoState
 
@@ -60,12 +60,30 @@ def test_a_system_tag_is_nobodys_to_edit(db, make_user):
     service.create_tag(db, other, "Theirs", "other", None)  # another user's tag stays theirs
     db.commit()
     assert queries.own_tag(db, user, system.id) is None
-    assert [t.id for t, _ in queries.tags_with_counts(db, user)] == [system.id]
+    assert [t.id for t, *_ in queries.tags_with_counts(db, user)] == [system.id]
 
 
 # --- tags ------------------------------------------------------------------------------------
 
 
+def test_a_tag_counts_apart_the_links_on_channels_the_user_still_follows(db, make_user):
+    """An unsubscribe keeps the channel's tag links; the Channels page's filter lists only followed
+    channels, so its count must not hold the others."""
+    user, other = make_user(), make_user()
+    tag = service.create_tag(db, user, "Music", "other", None)
+    for cid in ("UCa", "UCb", "UCgone"):
+        db.add(Channel(id=cid, title=cid))
+    db.flush()
+    for cid in ("UCa", "UCb"):
+        db.add(Subscription(user_id=user.id, channel_id=cid))
+    db.add(Subscription(user_id=other.id, channel_id="UCgone"))
+    for cid in ("UCa", "UCb", "UCgone"):
+        db.add(ChannelTag(channel_id=cid, tag_id=tag.id, user_id=user.id, source="user"))
+    db.commit()
+    [(_, count, subscribed)] = [r for r in queries.tags_with_counts(db, user) if r[0].id == tag.id]
+    assert (count, subscribed) == (3, 2)
+
+
 def test_a_tag_is_made_once_per_name_and_an_unknown_category_is_other(db, make_user):
     user = make_user()
     tag = service.create_tag(db, user, "Later", "nonsense", "#fff")