fix(macos): prevent crash when opening chat window

The app crashes when opening the chat window because the Textual
package's resource bundle (textual_Textual.bundle) isn't properly
embedded in release builds. When StructuredText tries to access
Bundle.module, it causes a fatal assertion failure.

This fix adds a runtime check to detect if the Textual bundle is
available before attempting to use StructuredText. If the bundle
is missing, the chat falls back to plain text rendering instead
of crashing.

The bundle availability check:
- Looks for textual_Textual.bundle in the main bundle
- Checks PlugIns and Frameworks directories
- Defaults to available in DEBUG builds (development)
- Falls back to plain Text view when unavailable

Fixes #1841
Related: #1640 (same root cause)

apps/shared/MoltbotKit/Sources/MoltbotChatUI/ChatMarkdownRenderer.swift

@@ -6,6 +6,43 @@ public enum ChatMarkdownVariant: String, CaseIterable, Sendable {
     case compact
 }
 
+/// Check if the Textual package's resource bundle is available.
+/// When running from a packaged app, the bundle may not be in the expected location,
+/// causing a fatal error when StructuredText tries to access Bundle.module.
+private let textualBundleAvailable: Bool = {
+    // The Textual package looks for its bundle at specific paths.
+    // Check if we can find it before attempting to use StructuredText.
+    let bundleName = "textual_Textual.bundle"
+
+    // Check in main bundle (packaged app)
+    if Bundle.main.path(forResource: "textual_Textual", ofType: "bundle") != nil {
+        return true
+    }
+
+    // Check in app's PlugIns or Frameworks directories
+    if let pluginsURL = Bundle.main.builtInPlugInsURL,
+       FileManager.default.fileExists(atPath: pluginsURL.appendingPathComponent(bundleName).path)
+    {
+        return true
+    }
+
+    if let frameworksURL = Bundle.main.privateFrameworksURL,
+       FileManager.default.fileExists(atPath: frameworksURL.appendingPathComponent(bundleName).path)
+    {
+        return true
+    }
+
+    // In development (SwiftPM), Bundle.module should work
+    // We can't directly test Bundle.module without triggering the crash,
+    // so we check for a known development path pattern
+    #if DEBUG
+    return true
+    #else
+    // In release builds, if we haven't found the bundle, assume it's not available
+    return false
+    #endif
+}()
+
 @MainActor
 struct ChatMarkdownRenderer: View {
     enum Context {
@@ -22,12 +59,20 @@ struct ChatMarkdownRenderer: View {
     var body: some View {
         let processed = ChatMarkdownPreprocessor.preprocess(markdown: self.text)
         VStack(alignment: .leading, spacing: 10) {
-            StructuredText(markdown: processed.cleaned)
-                .modifier(ChatMarkdownStyle(
-                    variant: self.variant,
-                    context: self.context,
-                    font: self.font,
-                    textColor: self.textColor))
+            if textualBundleAvailable {
+                StructuredText(markdown: processed.cleaned)
+                    .modifier(ChatMarkdownStyle(
+                        variant: self.variant,
+                        context: self.context,
+                        font: self.font,
+                        textColor: self.textColor))
+            } else {
+                // Fallback: render as plain text when Textual bundle is unavailable
+                Text(processed.cleaned)
+                    .font(self.font)
+                    .foregroundStyle(self.textColor)
+                    .textSelection(.enabled)
+            }
 
             if !processed.images.isEmpty {
                 InlineImageList(images: processed.images)