Give mixed selections something to do

A Drag of different kinds showed an empty wheel, because the catalog only
answers for a single category. Filee's answer is a mixed profile, so add
Zip (one archive, flat names) and Merge (non-PDFs are converted to PDF
first); a multi-file drag of one kind gets Zip too.

Sources/Konverter/Convert/ArchiveConverter.swift

@@ -58,6 +58,67 @@ enum ArchiveConverter {
         }
     }
 
+    /// Packs a whole selection into one ZIP, the way Finder's *Compress* does.
+    /// Inputs that live in the same folder keep their relative names; a
+    /// selection spanning folders is staged through symlinks so the archive
+    /// still has flat, readable entries instead of absolute paths.
+    static func createArchive(
+        from inputs: [URL],
+        at destination: URL,
+        cancellation: Cancellation? = nil,
+        progress: ((Double) -> Void)? = nil
+    ) throws {
+        guard !inputs.isEmpty else {
+            throw ConversionError.unsupported("There is nothing to archive.")
+        }
+        try cancellation?.check()
+        progress?(0.1)
+
+        let folders = Set(inputs.map { $0.deletingLastPathComponent().path })
+        if folders.count == 1, let folder = inputs.first?.deletingLastPathComponent() {
+            try Shell.run(
+                Toolchain.zip,
+                ["-r", "-X", destination.path] + inputs.map { $0.lastPathComponent },
+                currentDirectory: folder,
+                cancellation: cancellation
+            )
+            progress?(1)
+            return
+        }
+
+        let staging = FileManager.default.temporaryDirectory
+            .appendingPathComponent("konverter-zip-\(UUID().uuidString)", isDirectory: true)
+        try FileManager.default.createDirectory(at: staging, withIntermediateDirectories: true)
+        defer { try? FileManager.default.removeItem(at: staging) }
+
+        var names: [String] = []
+        for input in inputs {
+            var name = input.lastPathComponent
+            var index = 2
+            while names.contains(name) {
+                let ext = input.pathExtension
+                let base = input.deletingPathExtension().lastPathComponent
+                name = ext.isEmpty ? "\(base) \(index)" : "\(base) \(index).\(ext)"
+                index += 1
+            }
+            names.append(name)
+            try FileManager.default.createSymbolicLink(
+                at: staging.appendingPathComponent(name),
+                withDestinationURL: input
+            )
+        }
+
+        // `zip` follows symlinks unless asked for `-y`, so the archive holds
+        // the real files rather than links to them.
+        try Shell.run(
+            Toolchain.zip,
+            ["-r", "-X", destination.path] + names,
+            currentDirectory: staging,
+            cancellation: cancellation
+        )
+        progress?(1)
+    }
+
     /// Expands an archive into `directory`, returning the folder that callers
     /// should reveal.
     @discardableResult
@@ -117,10 +178,10 @@ enum ArchiveConverter {
         case "tar", "tgz":
             return try Shell.run(Toolchain.tar, ["-tf", source.path]).stdout
         case "gz":
-            let size = (try? FileManager.default.attributesOfItem(atPath: source.path)[.size] as? Int) ?? 0
+            let size = (try? FileManager.default.attributesOfItem(atPath: source.path))?[.size] as? Int ?? 0
             return """
             GZIP stream
-            Compressed size: \(ByteCountFormatter.string(fromByteCount: Int64(size ?? 0), countStyle: .file))
+            Compressed size: \(ByteCountFormatter.string(fromByteCount: Int64(size), countStyle: .file))
             Inner name: \(source.deletingPathExtension().lastPathComponent)
             """
         default: