Fix saturation analyzer V1 docs to match implementation (#987) (#991)

Align both saturation-analyzer.md and saturation-scaling-config.md with the
actual codebase. Key corrections:

- Scale-down simulation: rewrite to match the scale-factor approach used in
  isScaleDownSafe() instead of the previously documented summation method
- Transition blocking: document model-level blocking with both checks
  (desired!=current AND metrics!=current) instead of per-variant preservation
- Cascade prevention: clarify two-layer protection and that pending-replica
  checks only run when the model is stable
- ConfigMap key format: document actual {modelID}#{namespace} lookup used by
  resolveSaturationConfig() instead of arbitrary key names
- ConfigMap name: capacity-scaling-config → wva-saturation-scaling-config
- File paths: fix three wrong paths in Architecture section
- Default thresholds: clarify V1 has no hardcoded defaults (requires ConfigMap)
- Override inheritance: correct false claim that omitted fields inherit from
  default — overrides fully replace the default config
- Scale-up example: fix boundary math (0.10 < 0.10 is false with strict <)
- API Reference: fix struct name, field types, and method signatures
- Add min/max replica clamping and scale-down minimum guard documentation
- Fix broken cross-document link

Author: ev-shindin