fix(voice/consistency): vary stock formulas, vendor-balance orient.py, unify the loop

- Vary 11 instances of two boilerplate openers ("A generic X course…" /
  "Strip away X…") across 10 modules so they read as distinct, concrete prose;
  kept the few deliberate, voice-distinct uses; locked exemplars untouched.
- M23 orient.py: detect a vendor-balanced set of AI-instruction filenames
  (AGENTS.md/CLAUDE.md/GEMINI.md/.cursorrules/.cursor/rules/copilot-instructions)
  instead of singling out one vendor. Still runs.
- Render the collaboration loop consistently as seven stations
  (issue->branch->implementation->PR->review->merge->closed) in M25/M26 to match
  M11 and the syllabus.

Closes #48
Closes #49
Closes #51

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

modules/21-skills-teaching-the-ai-your-playbook/README.md

@@ -143,8 +143,7 @@ are more steps to get wrong, and more value in getting them right every time.
 
 ## The AI angle
 
-A generic automation course would call this "write a runbook." The AI-specific twist is what makes it
-land:
+On paper this is just "write a runbook." The AI-specific twist is what makes it land:
 
 - **The AI will execute the playbook, not just read it.** A runbook for a human is a reminder; a skill
   for an agent is something it *performs*. The precision pays off immediately — vague step, vague