Replace the Tags tab with a tag picker sheet

The tab bar drops from five to four; Tags now opens as a sheet from the +
in the library's filter strip, which is the control that was already
about adding a tag.

Picking a tag pins it as a filter tab rather than pushing to a separate
per-tag list. That made TagBookmarksView redundant — the filter tab shows
the same thing, in whichever layout you're already using — so it's gone.

This also fixes what the + could reach. The old inline menu listed tags
found on the loaded page, so it offered 21 of 96 tags, and once a tag
filter was active it collapsed to just the tags co-occurring with that
one — pinning a second unrelated tag was impossible. The sheet sources
names from the tags endpoint via a new BookmarksViewModel.loadAllTags(),
and counts still come from loaded bookmarks, so a tag we haven't paged in
shows no number rather than a wrong one.

The sheet is searchable, marks already-pinned tags with a check, and
picking a pinned tag selects that tab instead of duplicating it.

Verified by driving the UI: the tab bar is now Bookmarks/Sources/
Podcasts/Search, + opens the sheet with 42 rows where the old menu had
21, and picking "ai" pinned an "ai" tab. Suite passes.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01JgLHztZGaEHvS3KNeGQmRM

Marks/Views/Library/LibraryKit.swift

@@ -277,9 +277,11 @@ struct LibraryCard: View {
 struct LibraryTagStrip: View {
     @Binding var filters: [LibraryFilter]
     @Binding var selection: LibraryFilter.ID?
-    /// Tags available to pin that aren't already open.
-    let available: [String]
     var onChange: () -> Void = {}
+    /// Opens the tag picker. It replaced an inline Menu, which could only list
+    /// tags found on the loaded page — and once a tag filter was active, that
+    /// collapsed to the handful of tags co-occurring with it.
+    var onBrowseTags: () -> Void = {}
 
     @Namespace private var strip
 
@@ -294,20 +296,13 @@ struct LibraryTagStrip: View {
                     ForEach(filters) { filter in
                         tab(filter)
                     }
-                    Menu {
-                        ForEach(available, id: \.self) { tag in
-                            Button(tag) { add(tag: tag) }
-                        }
-                        if !filters.contains(where: { $0.tag == nil }) {
-                            Divider()
-                            Button("Everything") { add(tag: nil) }
-                        }
-                    } label: {
+                    Button { onBrowseTags() } label: {
                         Image(systemName: "plus")
                             .font(.system(size: 18, weight: .light))
                             .foregroundStyle(Paper.ink.opacity(0.6))
                             .frame(width: 50, height: 42)
                     }
+                    .buttonStyle(.plain)
                     .accessibilityLabel("Pin a tag")
                     Spacer(minLength: 0)
                 }
@@ -359,15 +354,6 @@ struct LibraryTagStrip: View {
         }
     }
 
-    private func add(tag: String?) {
-        let new = LibraryFilter(name: tag ?? "Everything", tag: tag)
-        withAnimation(.spring(duration: 0.35, bounce: 0.1)) {
-            filters.append(new)
-            selection = new.id
-        }
-        onChange()
-    }
-
     private func close(_ filter: LibraryFilter) {
         filters.removeAll { $0.id == filter.id }
         if selection == filter.id {