fix(config): delete the model-routing chain — nothing has called it since April (#119)

Closes #116.

Deletes config/models.yaml, internal/config/models.go (LoadModels, ModelFor),
its test, the ModelsFile field on Config, and SUPERVISOR_MODELS_FILE from
.env.example. Option A from the issue.

Merge-gate evidence: negative claim independently re-established (no Go, shell,
Dockerfile, k8s, CI or infra-repo caller); task check exit 0 across both
modules; CI run 7374 green on the PR head.

Co-authored-by: Mathias <mthbqv@gmail.com>

config/models.yaml

@@ -1,26 +0,0 @@
-# Model selection — first entry per skill is used.
-# Override per-call by passing model in the MCP tool args.
-# Model names come from LiteLLM /v1/models (host/name format).
-
-default_chain:
-  - iguana/qwen3-coder-next
-
-skills:
-  tdd:
-    chain:
-      - koala/qwen3-coder-30b
-  review:
-    chain:
-      - iguana/devstral
-  debug:
-    chain:
-      - iguana/deepseek-r1-14b
-  spec:
-    chain:
-      - koala/phi4-14b
-  retrospective:
-    chain:
-      - iguana/qwen3-coder-next
-  trainer:
-    chain:
-      - iguana/qwen3-coder-next