Phase 24: Rewrite all 50 tutorial exercises to BizTalk-style EIP labs + exams

[Copilot]

Tutorials used simple theoretical exercises and hardcoded test/project counts that don't scale with multiple contributors. Rewrote all 50 tutorials to use practical lab exercises focused on Enterprise Integration Patterns, scalability, and atomicity — modeled after Microsoft BizTalk certification courseware.

Test fix

• Fixed flaky ScatterGatherAsync_Timeout test — callback was invoked per publish instead of once, causing assertion failures

Tutorial code audit (9 fixes across 8 tutorials)

• 02: Removed hardcoded test/project counts from environment setup table
• 10: Added missing RequireDiscardTopic property to MessageFilterOptions snippet
• 14: Fixed field name _compensation → _compensationService, variable result → success
• 25: Fixed incomplete error message (added Current time: {now:O})
• 28: Replaced oversimplified ExecuteAsync with actual implementation (backpressure, cooldown)
• 32: Fixed => new() → = new() (readonly field init, not property)
• 42: Added missing "Next" navigation link
• 49: Fixed test method name, field name, assertion to match source
• 50: Removed hardcoded test count from production checklist

Exercise rewrite (all 50 tutorials, chunks 093–101)

Every tutorial's ## Exercises section replaced with:

• 🔬 Lab — hands-on scenario requiring the learner to extend or modify actual platform code, focused on EIP pattern mechanics, scalability concerns, or atomicity guarantees
• 📝 Exam — certification-style knowledge check (multiple choice, scenario analysis, architecture decisions) with answer key

No references to unit tests, test counts, or project counts anywhere in tutorials.