CAS: Feature request: Import file naming in alphanumeric

[jmavescodex-arch]

Summary

Sort the source file list in the target-text import file picker alphanumerically by filename, so files appear in a consistent, predictable order every time the picker opens.

Problem

When starting a target-text import, the source file picker displays available source files in no consistent order. This makes it hard to locate a specific file, since users can't rely on it being where they'd expect alphabetically. Selecting the correct file becomes a scanning exercise rather than a quick lookup, which slows down the import workflow.

Steps to reproduce:

1. Start a target-text import.
2. Open the source file picker.
3. Observe the order of files shown.

Acceptance Criteria

• Source files in the target-text import file list are sorted alphanumerically by filename by default.
• Sorting is consistent every time the file picker opens.
• QA can verify order by quickly locating a known filename in the expected A–Z/0–9 position.

Interface URL: https://airtable.com/appfEUXIPganSIP89/pagyewiWtbGAM67M4/recIl0ARGTTEND1IT?home=pagy8X7KblenRWOQD