chore: update in-repo references after repo rename to ai-workflow-course

Gitea repo renamed the-workflow-course -> ai-workflow-course. Update the two
references to the old slug/URL:
- README repo-layout tree root.
- Module 1 "Get the course materials" download URL (still Verify-before-publish
  for the eventual public/GitHub host).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01TfzV5QvtPDz8LJS3Pu5VLT

README.md

@@ -66,7 +66,7 @@ the reasoning behind the sequencing.
 ## Repo layout
 
 ```
-the-workflow-course/
+ai-workflow-course/
   README.md                 # this file
   AGENTS.md                 # committed AI instructions — dogfoods Module 5 (vendor-neutral name)
   the-workflow-syllabus.md  # the full course plan (source of truth for structure)