fix(templates): spec-draft-opus@1 route to Opus, not airouter/Qwen3.6

Was silently dispatching to Qwen3.6 via airouter despite the name;
live runs were timing out (exit_code=124), wedging four M41 auto-advance
concepts. Mirrors agent-runtimes commit acc5cbe5.

Claude-Session: https://claude.ai/code/session_012arAwUuBQrpnMzJ36mEVBk

task-templates/workflow/spec-draft-opus@1.yaml

@@ -1,7 +1,7 @@
 name: spec-draft-opus
 version: 1
 description: Draft a spec from an idea using spec-writer agent
-runtime: spec-writing-airouter-repo
+runtime: spec-writing-opus-repo
 input:
   state: idea
   tags_required: []
@@ -16,10 +16,8 @@ scope_budget:
 nodes:
   - id: agent
     kind: agent
-    template: spec-writing-airouter-repo
-    cli: agentic
-    model: Qwen3.6
-    labels: [airouter]
+    template: spec-writing-opus-repo
+    model: opus
     runtime_env:
       AGENT_REPO_URL: "git@gitea.oreillyit.nz-ai-enablement:skynet/agent-runtimes-agents.git"
       AGENT_BRANCH: "spec/auto-draft"