Give the single-branch switch picker its disabled explanatory row

With branch creation relocated to the settings sheet, a single-branch
board's switch menu opened onto nothing and read as broken (ruled
2026-08-06, built with the Git tab): a bare Text — AppKit's standard
disabled item, read by VoiceOver as disabled text — now says "No other
branches" where the switch entries would be. The filter behind it becomes
the pure switchTargets(branches:current:) seam, pinned by
BranchSwitchTargetTests: current excluded, nil current passes all through,
repository order preserved.

Claude-Session: https://claude.ai/code/session_01SR4XGjmBE16ZUYWpfFHXwY

Kanban/UI/Board/BoardGitControls.swift

@@ -67,7 +67,7 @@ struct BoardGitBranchSurface: Equatable {
     /// loud failure, ruled 2026-07-31: "with the whole git surface paused … and the popover's git
     /// section naming the state").
     ///
-    /// A sibling of the nested and unverifiable notes (`BoardInfoPopover`) and written in their
+    /// A sibling of the nested and unverifiable notes (`BoardGitTabView`) and written in their
     /// register — one sentence, the state first and the consequence after — rather than the pause
     /// note's two lines, because both of *those* lines would be wrong here: nothing is "in
     /// progress", and there is no tool whose job it is to finish it. What it keeps from the pause
@@ -169,22 +169,44 @@ struct BoardGitControls: View {
     /// beside it.
     ///
     /// **Switch entries and nothing else** since the 2026-07-31 split — the "New Branch…" entry that
-    /// used to close the menu is the settings sheet's standing Create field now. On a board with one
-    /// branch the menu is therefore *empty*, and that is left honest rather than papered over: the
-    /// label still reads the current branch and still disables with the rest of the git surface, so
-    /// the line goes on saying the one thing it is here to say.
+    /// used to close the menu is the settings sheet's standing Create field now. **A single-branch
+    /// board therefore opens onto a disabled explanatory row** (03-board-ui.md ▸ Board popover ▸ Git
+    /// tab, ruled 2026-08-06 and built with the tab): the earlier posture left the menu genuinely
+    /// empty and called that honest, but honest is not the same as legible — a menu that opens onto
+    /// nothing reads as broken, not as complete.
     private var branchRow: some View {
-        HStack(spacing: 6) {
+        // Resolved once and handed to both halves of the menu builder: the emptiness *is* the
+        // condition being rendered, so asking twice would be asking the same question of a store
+        // that could answer differently between the two reads.
+        let targets = otherBranches
+
+        return HStack(spacing: 6) {
             Image(systemName: "arrow.triangle.branch")
                 .imageScale(.small)
                 .foregroundStyle(.secondary)
 
             Menu {
-                ForEach(otherBranches, id: \.self) { name in
+                if targets.isEmpty {
+                    // **The single-branch board's row** (03-board-ui.md ▸ Board popover ▸ Git tab,
+                    // ruled 2026-08-06). It teaches the two things an empty menu leaves a user to
+                    // guess at: *why* there is nothing to pick — this menu holds only the **other**
+                    // local branches, and there are none — and, by standing where "New Branch…" used
+                    // to, that creation is no longer here at all; it is the settings sheet's Create
+                    // field, one row down through Board Settings…
+                    //
+                    // A bare `Text` inside a `Menu` is AppKit's standard disabled item: greyed,
+                    // unclickable, and read by VoiceOver as disabled text rather than as an
+                    // actionable row — which is exactly the register a sentence explaining an absence
+                    // wants (06 ▸ Rules: teach, never look broken; never a disabled button pretending
+                    // to be a control).
+                    Text("No other branches")
+                } else {
+                    ForEach(targets, id: \.self) { name in
                         Button(name) {
                             Task { await git.switcher?.switchTo(name) }
                         }
                     }
+                }
             } label: {
                 Text(surface.branchLabel)
                     .font(.callout)
@@ -204,10 +226,32 @@ struct BoardGitControls: View {
         }
     }
 
-    /// Every local branch except the one already checked out — a picker offering the current branch
-    /// would be offering a no-op, and the switch refuses one anyway.
+    /// This board's switch targets, off the live switcher — see `switchTargets(branches:current:)`
+    /// for the rule itself.
     private var otherBranches: [String] {
-        (git.switcher?.branches ?? []).filter { $0 != git.branch }
+        Self.switchTargets(branches: git.switcher?.branches ?? [], current: git.branch)
+    }
+
+    /// **Every local branch except the one already checked out** — a picker offering the current
+    /// branch would be offering a no-op, and the switch refuses one anyway
+    /// (`BranchSwitchSequenceTests`' "a switch to the branch already checked out does nothing").
+    ///
+    /// A pure static seam rather than a computed property alone, for `BoardGitBranchSurface.resolve`'s
+    /// reason one level up: the *rule* is the part worth pinning (`BranchSwitchTargetTests`) and the
+    /// `Menu` it fills is SwiftUI. It is also the predicate the disabled "No other branches" row hangs
+    /// on (03-board-ui.md ▸ Board popover ▸ Git tab, 2026-08-06), which makes "when is that row
+    /// shown" a question with one testable answer rather than a shape buried in a view builder.
+    ///
+    /// A `nil` `current` — the moment before the first branch read answers — passes every branch
+    /// through rather than none: the list is a set of candidates, and the switch's own gate is what
+    /// decides whether one can be taken. `nonisolated` because nothing here touches the view: a pure
+    /// filter over plain values, reachable from a test with no actor to hop to.
+    ///
+    /// The repository's own ordering survives untouched — `GitBranchOperation.localBranches` is what
+    /// libgit2 listed, and a picker that re-sorted it would be inventing an order the repository
+    /// never had.
+    nonisolated static func switchTargets(branches: [String], current: String?) -> [String] {
+        branches.filter { $0 != current }
     }
 
     // MARK: The pause

KanbanTests/BranchSwitchTests.swift

@@ -661,7 +661,7 @@ struct BranchSwitchSequenceTests {
         var asked = 0
         switcher.settleSessions = { asked += 1; return .proceed }
 
-        // The picker never offers it (`BoardGitControls.otherBranches`), and the operation is a no-op
+        // The picker never offers it (`BoardGitControls.switchTargets`), and the operation is a no-op
         // if one ever arrives: same branch, same tree, nothing to announce.
         #expect(await switcher.switchTo("main"))
         #expect(GitRepository.branchName(at: fixture.root) == "main")
@@ -1038,6 +1038,55 @@ struct BoardGitBranchSurfaceTests {
     }
 }
 
+// MARK: - The switch picker's targets
+
+/// **What the branch menu offers, and what it says when that is nothing** (03-board-ui.md ▸ Board
+/// popover ▸ Git tab).
+///
+/// `BoardGitControls.switchTargets` is the filter as a pure function, pinned here for the reason
+/// `BoardGitBranchSurface.resolve` is pinned above: the rule is the part worth asserting, and the
+/// `Menu` it fills is SwiftUI. Its emptiness is load-bearing since 2026-08-06 — with branch
+/// *creation* relocated to the settings sheet, an empty result is what puts the disabled "No other
+/// branches" row on screen in place of a menu that would otherwise open onto nothing and read as
+/// broken.
+@Suite("Board popover ▸ the switch picker's targets")
+struct BranchSwitchTargetTests {
+
+    @Test("The branch already checked out is never offered — switching to it would be a no-op")
+    func theCurrentBranchIsExcluded() {
+        #expect(
+            BoardGitControls.switchTargets(branches: ["main", "redesign", "spike"], current: "main")
+                == ["redesign", "spike"]
+        )
+    }
+
+    @Test("A single-branch board has no targets at all — which is what the disabled row is for")
+    func aSingleBranchBoardHasNoTargets() {
+        #expect(BoardGitControls.switchTargets(branches: ["main"], current: "main").isEmpty)
+        // The shape a repository with an unborn HEAD is in: no branches listed at all.
+        #expect(BoardGitControls.switchTargets(branches: [], current: "main").isEmpty)
+    }
+
+    @Test("Before the first branch read every branch is a candidate, rather than none")
+    func anUnreadCurrentPassesEverythingThrough() {
+        // `HistoryStore.branch` is `nil` until `refreshBranch()` answers, which is a moment the
+        // popover is on screen for. Filtering everything out there would be a menu that starts empty
+        // and fills in — the switch's own gate is what decides whether a target can be taken.
+        #expect(
+            BoardGitControls.switchTargets(branches: ["main", "redesign"], current: nil)
+                == ["main", "redesign"]
+        )
+    }
+
+    @Test("The repository's own order survives — the picker never re-sorts what libgit2 listed")
+    func orderIsPreserved() {
+        #expect(
+            BoardGitControls.switchTargets(branches: ["zeta", "alpha", "main", "beta"], current: "main")
+                == ["zeta", "alpha", "beta"]
+        )
+    }
+}
+
 // MARK: - Commit identity
 
 @Suite("Board popover ▸ the commit-identity fields")