The loader collects every fail-fast defect and honors per-open skips

Phase 1 of the decision surface (01 ▸ Malformed input, settled
2026-07-31): BoardLoadFailure aggregates the walk's defects in walk
order — stop-at-first retires. Environmental failures (unreadable root,
not-a-directory) stay immediate single-defect throws: there is no walk
to collect from. A defective root index is recorded and the walk
continues into the children (nothing in the walk consults the parsed
root document — verified); a defective lane, card, or trash-entry index
records and skips its subtree, Re-check's whole-walk re-aggregation
being the designed loop for what hides beneath. load(skipping:) is the
per-open skip channel: a skipped path's item is omitted from the model
and surfaces as LoadWarning.userSkipped; root paths are unskippable by
construction. The reload-breakage banner carries the aggregate ("…and
N more"), single-defect sentences byte-identical to before. Two new
multi-defect fixture boards; suite 2591 green.

Claude-Session: https://claude.ai/code/session_01CqjXB7ASoWtbyoGod68k97

KanbanTests/BoardStoreRegistryTests.swift

@@ -204,12 +204,12 @@ struct BoardStoreRegistryTests {
         try fixture.item(Ident.lane1, brokenIndex)
         let registry = BoardStoreRegistry()
 
-        do throws(BoardLoadError) {
+        do throws(BoardLoadFailure) {
             _ = try registry.acquire(fixture.root)
             Issue.record("expected the load to fail fast")
         } catch {
-            if case .unparseableYAML = error.reason {} else {
-                Issue.record("expected unparseable YAML, got \(error.reason)")
+            if case .unparseableYAML = error.primary.reason {} else {
+                Issue.record("expected unparseable YAML, got \(error.primary.reason)")
             }
         }
 
@@ -265,15 +265,15 @@ struct BoardStoreRegistryTests {
         let missing = FileManager.default.temporaryDirectory
             .appendingPathComponent("no-such-board-\(UUID().uuidString)", isDirectory: true)
 
-        do throws(BoardLoadError) {
+        do throws(BoardLoadFailure) {
             _ = try registry.acquire(missing)
             Issue.record("expected a missing root to fail")
         } catch {
             // The identity read fails first, and the registry deliberately says nothing about that —
             // it lets `BoardStore`'s load produce the honest reason.
-            #expect(error.path == ".")
-            if case .unreadableRoot = error.reason {} else {
-                Issue.record("expected an unreadable root, got \(error.reason)")
+            #expect(error.primary.path == ".")
+            if case .unreadableRoot = error.primary.reason {} else {
+                Issue.record("expected an unreadable root, got \(error.primary.reason)")
             }
         }
         #expect(registry.openBoardCount == 0)