feat(omp): add claude-fable-5 to vibeproxy models

Register VibeProxy's claude-fable-5 (Anthropic) as a selectable
vibeproxy/claude-fable-5 option. Extended thinking verified against the
proxy (returns a thinking block), so reasoning is enabled to match the
other Claude entries. Option-only: no modelRoles, smolModel, or fallback
chains touched.

Author: edmundmiller

config/omp/models.yml

@@ -35,3 +35,7 @@ providers:
       - id: claude-haiku-4-5-20251001
         name: VibeProxy Claude Haiku 4.5
         contextWindow: 200000
+      - id: claude-fable-5
+        name: VibeProxy Claude Fable 5
+        contextWindow: 200000
+        reasoning: true