A reserved key comes to life — the card window's sidebar grows a Labels section, and labels stops being somebody else's

`labels` has been a reserved tracker key since the rewrite: preserved verbatim, never
interpreted, drawn only as an anonymous row in the Details section beside `assignees` and
`due`. The owner's cards claim it for first-party use, so it joins the schema — read
leniently (a list of names, a bare scalar coercing to one, a mapping malformed and
preserved), written canonically (a quoted flow list in the order the user arranged, no
auto-sort), and removed outright when the last label goes, the way an expanded lane drops
`collapsed`.

Identity is case-insensitive and display is case-preserving, so a card carries `bug` once
however many ways the board spells it, and entries the reading cannot name ride through the
write untouched at the tail.

The section sits second, above Details — which is the point rather than a layout preference:
Details is where keys the app does *not* own are shown, and this key just stopped being one.
Rows rather than chips, because the sidebar is twenty-six characters wide. The add field
autocompletes against the board's own used-labels universe, derived from every live and
trashed card with no store beside the files, and says out loud when Return would mint a word
the board has never used.

Writes ride a `.relabel` operation of their own, because the commit composer has said
"Relabel card 'X'" since long before there was a control to press — and now the undo row says
it too.

Claude-Session: https://claude.ai/code/session_014PtZdPwqZuqEDLc6wZMtEy

Kanban/UI/Card/CardWindowView.swift

@@ -84,6 +84,10 @@ struct CardWindowView: View {
     /// Controls) — app state, not board state, which is why it arrives beside the store rather than
     /// on it.
     let recents: StyleRecents
+    /// The app-wide recently-applied labels the Labels section feeds (`LabelRecents`;
+    /// `FrontmatterKeys.labels`) — `recents`' neighbour in every respect, app state rather than board
+    /// state, arriving beside the store for that field's reason exactly.
+    let labelRecents: LabelRecents
     /// The card's folder on disk — what relative images and links in the body resolve against
     /// (05 ▸ Preview). `nil` only where a caller has no board root to build it from.
     let cardFolder: URL?
@@ -449,8 +453,8 @@ struct CardWindowView: View {
 
     // MARK: - Attributes sidebar
 
-    /// The sidebar's sections: **Style, Details, Attachments** — Attachments at the bottom of the
-    /// stack (reordered 2026-08-09, Pipeline card 8f26b029), Actions gone entirely (retired the same
+    /// The sidebar's sections: **Style, Labels, Details, Attachments** — Attachments at the bottom of
+    /// the stack (reordered 2026-08-09, Pipeline card 8f26b029), Actions gone entirely (retired the same
     /// day, Pipeline card bcd3b323): its Delete and Reveal in Finder are now the card window's own
     /// toolbar items (`CardToolbar`), reachable from Customize and, for Delete, on by default. This
     /// is exactly the `VStack`'s child order, so keyboard Tab order and VoiceOver's reading order
@@ -462,10 +466,15 @@ struct CardWindowView: View {
     /// with Actions at the bottom — an owed amendment, tracked on the two cards' own threads rather
     /// than made here.
     ///
-    /// One of the two remaining sections is conditional, and the condition is the section's own
-    /// rather than a rule restated here: **Details** renders nothing when the card carries no unknown
-    /// frontmatter keys ("shown only when any exist"). Style and Attachments are unconditional, so
-    /// the composition a user learns on one card is the composition they get on the next.
+    /// One of the four sections is conditional, and the condition is the section's own rather than a
+    /// rule restated here: **Details** renders nothing when the card carries no unknown frontmatter
+    /// keys ("shown only when any exist"). Style, Labels and Attachments are unconditional, so the
+    /// composition a user learns on one card is the composition they get on the next.
+    ///
+    /// **Labels joined 2026-08-09** (Pipeline card a4462d28), sitting second — see
+    /// `CardLabelsSection`'s own doc comment for why it goes after Style and, load-bearingly, *above*
+    /// Details: `labels` stopped being an unknown key that day, and Details is the section for keys the
+    /// app does not own.
     ///
     /// The History section that once sat between Details and Actions left with app-managed git
     /// (strategy/01-git-excision.md, 2026-08-08); View ▸ History (`FutureCommands.swift`) is the only
@@ -475,6 +484,16 @@ struct CardWindowView: View {
             VStack(alignment: .leading, spacing: bodyPointSize * 1.25) {
                 CardStyleSection(store: store, recents: recents, cardID: card.id, undo: undo)
 
+                // The snapshot's own reading, not a store lookup: this window's `Card` is the value
+                // the last reload produced, and every other section here renders off it.
+                CardLabelsSection(
+                    store: store,
+                    recents: labelRecents,
+                    cardID: card.id,
+                    labels: card.labels.value ?? [],
+                    undo: undo
+                )
+
                 // The snapshot's own document, not a re-read: the loader parsed this file, unknown
                 // keys and their order included, and `Card` has carried it since (`BoardModel`).
                 CardDetailsSection(rows: CardDetails.rows(of: card.document))