feat: render native chat markdown via Textual

apps/shared/ClawdbotKit/Sources/ClawdbotChatUI/ChatMarkdownPreprocessor.swift

@@ -0,0 +1,51 @@
+import Foundation
+
+enum ChatMarkdownPreprocessor {
+    struct InlineImage: Identifiable {
+        let id = UUID()
+        let label: String
+        let image: ClawdbotPlatformImage?
+    }
+
+    struct Result {
+        let cleaned: String
+        let images: [InlineImage]
+    }
+
+    static func preprocess(markdown raw: String) -> Result {
+        let pattern = #"!\[([^\]]*)\]\((data:image\/[^;]+;base64,[^)]+)\)"#
+        guard let re = try? NSRegularExpression(pattern: pattern) else {
+            return Result(cleaned: raw, images: [])
+        }
+
+        let ns = raw as NSString
+        let matches = re.matches(in: raw, range: NSRange(location: 0, length: ns.length))
+        if matches.isEmpty { return Result(cleaned: raw, images: []) }
+
+        var images: [InlineImage] = []
+        var cleaned = raw
+
+        for match in matches.reversed() {
+            guard match.numberOfRanges >= 3 else { continue }
+            let label = ns.substring(with: match.range(at: 1))
+            let dataURL = ns.substring(with: match.range(at: 2))
+
+            let image: ClawdbotPlatformImage? = {
+                guard let comma = dataURL.firstIndex(of: ",") else { return nil }
+                let b64 = String(dataURL[dataURL.index(after: comma)...])
+                guard let data = Data(base64Encoded: b64) else { return nil }
+                return ClawdbotPlatformImage(data: data)
+            }()
+            images.append(InlineImage(label: label, image: image))
+
+            let start = cleaned.index(cleaned.startIndex, offsetBy: match.range.location)
+            let end = cleaned.index(start, offsetBy: match.range.length)
+            cleaned.replaceSubrange(start..<end, with: "")
+        }
+
+        let normalized = cleaned
+            .replacingOccurrences(of: "\n\n\n", with: "\n\n")
+            .trimmingCharacters(in: .whitespacesAndNewlines)
+        return Result(cleaned: normalized, images: images.reversed())
+    }
+}