Relocate loose card files into attachments

01's Lanework-owns-the-board carve-out: a regular file beside a card's
index.md belongs in attachments/, and the app moves it there. The
loader detects read-only — a new LoadResult.looseCardFiles channel,
separate from the stray-tolerance warnings because it says the opposite
thing — skipping directories, symlinks, hidden entries, and the
reserved names compared case-insensitively (on APFS, Index.md IS the
index). The relocation rides one performWrite bracket at the tail of
every successful reload, which makes lock deferral free: the reload
that lifts a read-only lock is the reload that relocates. A
lane/card/filename memo keeps a failing relocation from hot-looping —
one one-shot, then silence until disk changes. The notice rides the
loss-row class, phrasing folded by BannerCenter (one file, one card's
files, a multi-card sweep), naming original filenames per the
importAttachment rule. Paste normalizes at the import boundary: staged
snapshots' loose files land in the pasted card's attachments silently,
every arrival path declaring its side via an explicit
normalizingLooseFiles parameter — drag paths decline and fall back to
the destination's own carve-out. checkIsCardFolder closes the hole
where a lane's notes.txt would have been relocated: card depth is
exact, UUID under UUID.

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

Kanban/App/ClipboardStore.swift

@@ -320,6 +320,15 @@ public final class ClipboardStore {
     /// does rather than earning a sub-rule for the one case where the items were already on this
     /// board. It is cleared here rather than at ⌘V so the two staleness guards keep their meaning: a
     /// paste the pasteboard moved under lands nothing, and so clears nothing.
+    ///
+    /// **A paste is an import boundary, so normalization applies** (04 ▸ Clipboard, settled
+    /// 2026-07-28 — 01-storage-format.md's loose-file carve-out): every arrival below passes
+    /// `normalizingLooseFiles: true`, so a loose file the staged snapshot faithfully carried beside
+    /// a card's `index.md` lands inside the pasted card's `attachments/`, Finder-renamed on
+    /// collision. Both branches and both operations, unqualified, because 04's sentence is
+    /// unqualified. Nothing is dropped and nothing is announced: the snapshot preserved the file,
+    /// the paste kept it, and it is where the schema says it belongs — the carve-out's notice is for
+    /// files the app moves *without* being asked, which is the loader's path, not this one.
     private func perform(_ manifest: ClipboardManifest, plan: Plan, into store: BoardStore) {
         refresh()
         // The pasteboard moved under this paste (another app copied while the chain settled): the
@@ -338,10 +347,17 @@ public final class ClipboardStore {
                     operation: .move,
                     toLane: target.laneID,
                     at: target.index,
-                    clearingTombstones: false
+                    clearingTombstones: false,
+                    normalizingLooseFiles: true
                 )
             case let .lanes(index):
-                store.receiveLanes(sources, operation: .move, at: index, clearingTombstones: false)
+                store.receiveLanes(
+                    sources,
+                    operation: .move,
+                    at: index,
+                    clearingTombstones: false,
+                    normalizingLooseFiles: true
+                )
             }
             consumeCut()
             return
@@ -383,14 +399,16 @@ public final class ClipboardStore {
                 operation: .copy,
                 toLane: target.laneID,
                 at: target.index,
-                clearingTombstones: clearingTombstones
+                clearingTombstones: clearingTombstones,
+                normalizingLooseFiles: true
             )
         case let .lanes(index):
             store.receiveLanes(
                 sources,
                 operation: .copy,
                 at: index,
-                clearingTombstones: clearingTombstones
+                clearingTombstones: clearingTombstones,
+                normalizingLooseFiles: true
             )
         }
         store.banners.postDegradedPaste(losses)