Clarify VRAM eviction rule for cross-priority edge case

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

kischdle/llmux/docs/superpowers/specs/2026-04-03-llmux-design.md

@@ -93,7 +93,7 @@ When a request arrives for a model whose physical model is not loaded:
    - Evict LLM first
    - Evict TTS second
    - Evict ASR only as last resort
-   - Never evict a higher-priority model to load a lower-priority one
+   - Never evict a higher-priority model to load a lower-priority one (e.g., never evict ASR to make room for TTS; in that case, evict the LLM instead)
 4. Load the requested model.
 
 ### Concurrency