Comments, phase 2 — the pane, the composer, and the inline session

The card window recomposes into three componentized panes (body,
comments, attributes) with two mounts — beside or body-over-comments
at ~3:2 — behind View ▸ Comments Beside Body. View ▸ Show Comments is
one persisted app-wide bit, no content-derived auto-show; File ▸ Add
Comment flips it on and focuses the composer. The thread renders
author lines, edited markers, card-subset Markdown bodies, and
read-only Quick Look chips under a count header with the sort-
direction control. The composer edits comments/.draft/ on the slow
cadence (blur, close, quit, ~30s interval), Escape only moves focus,
⌘↩ posts. Inline edit is a body-edit session in miniature: 700ms
debounce, Save/⌘↩ commits, Cancel and Escape revert to session-start
bytes, close flushes. File drops within either authoring surface
carve out of the window-wide card default into that surface's
attachments/; paperclips cover the no-drag path. Close flush runs
inline flush, then draft save, then the comments/.trash purge;
open sweeps crash residue.

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

Kanban/Storage/BoardWriter.swift

@@ -1852,13 +1852,35 @@ public enum BoardWriter: Sendable {
         try checkIsDirectory(cardFolder, describedAs: "card folder", operation: batchOperation)
         try checkIsUUIDShaped(cardFolder, operation: batchOperation)
 
-        let attachmentsFolder = cardFolder.appendingPathComponent(attachmentsFolderName, isDirectory: true)
+        return try importFiles(sourceURLs, intoAttachmentsOf: cardFolder, batchOperation: batchOperation)
+    }
+
+    /// **Steps 2–4 of `importAttachments`, with the shape guard left to the caller** — the copy
+    /// itself, which is identical wherever an `attachments/` folder hangs.
+    ///
+    /// It exists because a *comment* has an `attachments/` too (01-storage-format.md § Enhanced
+    /// schema — "a card's anatomy one level down"), and comment attachments author in-window
+    /// (05-card-window.md ▸ The comments column, ruled 2026-07-29). The alternative was a second
+    /// importer beside this one, which is exactly what `CardAttachments`' own note forbids for the
+    /// card level: "one import path, one set of banners, one Finder-style collision rename". The
+    /// generalization is therefore the *smallest* one that keeps that true — the folder shape is what
+    /// differs between a card and a comment, and it is the only thing the callers still decide.
+    ///
+    /// Everything the batch promises is here rather than at either entry point: `attachments/` minted
+    /// on first import, each source validated before it is touched, the Finder-style collision-free
+    /// name, the non-atomic copy with best-effort cleanup, and the import receipt.
+    static func importFiles(
+        _ sourceURLs: [URL],
+        intoAttachmentsOf itemFolder: URL,
+        batchOperation: WriteOperation
+    ) throws(BoardWriteError) -> [ImportedAttachment] {
+        let attachmentsFolder = itemFolder.appendingPathComponent(attachmentsFolderName, isDirectory: true)
         do {
             try FileManager.default.createDirectory(at: attachmentsFolder, withIntermediateDirectories: true)
         } catch {
             throw BoardWriteError(
                 operation: batchOperation,
-                path: cardFolder.path,
+                path: itemFolder.path,
                 reason: .io(message: "could not create attachments folder: \(error.localizedDescription)")
             )
         }
@@ -2325,9 +2347,24 @@ public enum BoardWriter: Sendable {
         try checkIsDirectory(cardFolder, describedAs: "card folder", operation: operation)
         try checkIsUUIDShaped(cardFolder, operation: operation)
 
-        guard BoardLoader.attachmentNames(in: cardFolder).contains(name) else { return nil }
+        return try trashAttachment(named: name, fromItemFolder: cardFolder, operation: operation)
+    }
 
-        let fileURL = cardFolder
+    /// `removeAttachment`'s body with the shape guard left to the caller — `importFiles`' split, for
+    /// its reason: a comment's authoring chips carry Remove too, "to the **system** Trash — the
+    /// sidebar row's rule" (05-card-window.md ▸ The comments column), and one Trash-not-delete
+    /// promise is worth more than two implementations of it.
+    ///
+    /// The listing check, the never-hard-delete guarantee and the a-name-that-is-gone-is-not-a-failure
+    /// rule all live here, so they hold at both levels without either caller restating them.
+    static func trashAttachment(
+        named name: String,
+        fromItemFolder itemFolder: URL,
+        operation: WriteOperation
+    ) throws(BoardWriteError) -> URL? {
+        guard BoardLoader.attachmentNames(in: itemFolder).contains(name) else { return nil }
+
+        let fileURL = itemFolder
             .appendingPathComponent(attachmentsFolderName, isDirectory: true)
             .appendingPathComponent(name)
         var trashedURL: NSURL?