feat(routing): add tiers.yaml + rename spec/review-arch templates to airouter

W1 stage-routing work:
- model-registry/tiers.yaml: defines planning/spec-test/coding tier floors
  (complexity≥9/creativity≥9/context≥9 | spec_adherence≥9/test_pass_rate≥9 |
  spec_adherence≥7/test_pass_rate≥7) with qualifies_today lists
- spec-draft-airouter@2.yaml: honest name for what was spec-draft-opus@1
  (always ran Qwen3.6/airouter, not Opus)
- review-spec-arch-airouter@1.yaml: honest name for review-spec-arch-opus@1

Old @1 files kept for in-flight task backward-compatibility.

Claude-Session: https://claude.ai/code/session_01B35bPAKv5uyW1F9gzMcRN7

task-templates/workflow/spec-draft-airouter@2.yaml

@@ -0,0 +1,47 @@
+name: spec-draft-airouter
+version: 2
+description: Draft a spec from an idea using spec-writer agent
+runtime: spec-writing-airouter-repo
+input:
+  state: idea
+  tags_required: []
+  tags_forbidden: [security-sensitive]
+  required_artifacts: []
+output:
+  state: spec-draft
+scope_budget:
+  files_modified_max: 5
+  lines_diff_max: 300
+  wall_clock_seconds_max: 3600
+nodes:
+  - id: agent
+    kind: agent
+    template: spec-writing-airouter-repo
+    cli: agentic
+    model: Qwen3.6
+    labels: [airouter]
+    runtime_env:
+      AGENT_REPO_URL: "git@gitea.oreillyit.nz-ai-enablement:skynet/agent-runtimes-agents.git"
+      AGENT_BRANCH: "spec/auto-draft"
+    prompt: |
+      The agent-runtimes project repo is cloned at /workspace/project.
+      Change to that directory before doing any work.
+
+      Draft a spec for the following concept and commit it to the repo.
+
+      **Title**: ${item.title}
+
+      ${item.body}
+
+      Steps:
+      1. cd /workspace/project
+      2. Read existing specs in spec/ to understand the format
+      3. Create a slug from the title (lowercase, hyphens instead of spaces)
+      4. Write the spec to spec/<slug>.md following the project spec format
+      5. git add spec/<slug>.md && git commit -m "spec: auto-draft ${item.title}" && git push
+      6. Call task_complete with a one-sentence summary
+
+      The spec should have numbered requirement IDs, clear acceptance criteria,
+      and error handling. Follow the format of existing specs in spec/.
+escalation:
+  scope_exceeded: replan-spec-opus