Remove docs for deleted scheduler features (checkpoint, redundancy, telemetry, learning)

Matches HORUS scheduler cleanup that removed ~7,400 LOC of speculative features:
- Delete checkpoint.mdx, redundancy.mdx, telemetry.mdx pages
- Remove enable_learning() API docs and all learning phase references
- Remove AsyncIO/AutoAdaptive execution mode sections
- Simplify scheduling-intelligence to tier annotations + offline profiler only
- Update architecture diagram to Sequential/Parallel only
- Fix all See Also links to removed pages
- Update safety_critical() description (no more triple redundancy)
- Update benchmarks to reflect current tier system

Author: neos-builder

content/docs/advanced/blackbox.mdx

@@ -283,5 +283,4 @@ if anomalies.len() > previous_count {
 
 - [Safety Monitor](/advanced/safety-monitor) - Real-time safety monitoring
 - [Circuit Breaker](/advanced/circuit-breaker) - Fault tolerance patterns
-- [Checkpoint System](/advanced/checkpoint) - State persistence
 - [Troubleshooting](/troubleshooting) - Common issues and solutions

content/docs/advanced/checkpoint.mdx

@@ -324,4 +324,3 @@ if new_state != prev_state {
 
 - [BlackBox Flight Recorder](/advanced/blackbox) - Event logging
 - [Safety Monitor](/advanced/safety-monitor) - Real-time safety
-- [Checkpoint System](/advanced/checkpoint) - State recovery