Add Revert to Original flow and compression status report for Writer video

Allow users to revert a compressed video to the original and try a different
preset. The original is backed up to temp storage when disk space permits (10x
headroom). After compression, a summary row shows size reduction, elapsed time,
and average fps. Backup and summary are cleaned up on revert, delete, or window
close. Disk space is checked before compression with a blocking alert when
insufficient.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: livid

Planet/Entities/DraftModel.swift

@@ -342,10 +342,23 @@ class DraftModel: Identifiable, Equatable, Hashable, Codable, ObservableObject {
         _ attachment: Attachment,
         withCompressedVideoAt compressedURL: URL,
         compressionPreset: String
+    ) throws -> Attachment {
+        try replaceVideoAttachment(
+            attachment,
+            withVideoAt: compressedURL,
+            compressionPreset: compressionPreset
+        )
+    }
+
+    @discardableResult
+    func replaceVideoAttachment(
+        _ attachment: Attachment,
+        withVideoAt videoURL: URL,
+        compressionPreset: String?
     ) throws -> Attachment {
         let oldName = attachment.name
         let oldPath = attachment.path
-        let newAttachment = try addAttachment(path: compressedURL, type: .video)
+        let newAttachment = try addAttachment(path: videoURL, type: .video)
         newAttachment.videoCompressionPreset = compressionPreset
 
         if oldName != newAttachment.name {