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)
d0eb74195a