pipeline model routing: mechanical stages to MiniMax M3, spec stages to Fable low effort

- scaffolding-repo + test-writing-repo: anthropic-cloud-paul-oauth -> minimax + minimax-m3-max
- merge@1: new best-practices-minimax-repo composite (impl-review stays Sonnet)
- spec-draft-opus@1: Opus -> Fable 5 low effort via new fable-low-effort/v1
  env context (ANTHROPIC_MODEL=claude-fable-5, MAX_THINKING_TOKENS=1024) +
  spec-writing-fable-low-repo composite
- review-spec-arch-opus@1: Qwen3.6/airouter -> Fable 5 low effort via
  best-practices-fable-low-repo (arch review was on the cheapest model)

Template names kept (trigger rules reference them). Node model: fields
removed where env pins the model — a --model flag overrides ANTHROPIC_MODEL.

Claude-Session: https://claude.ai/code/session_019tJk7P8tZzJ24PvtgoGhLN

harnesses/composites/best-practices-fable-low-repo/v1/harness.yaml

@@ -0,0 +1,11 @@
+kind: composite
+name: best-practices-fable-low-repo
+version: 1
+description: "Best practices / spec review agent on Fable 5 (low effort) + repo clone via SSH"
+
+layers:
+  - context: best-practices/v1
+  - context: anthropic-cloud-paul-oauth/v1
+  - context: fable-low-effort/v1
+  - context: gitea-ssh/v1
+  - context: agent-repo/v1

harnesses/composites/best-practices-minimax-repo/v1/harness.yaml

@@ -0,0 +1,11 @@
+kind: composite
+name: best-practices-minimax-repo
+version: 1
+description: "Best practices review agent on MiniMax M3 (max effort) + repo clone via SSH — mechanical review/merge stages"
+
+layers:
+  - context: best-practices/v1
+  - context: minimax/v1
+  - context: minimax-m3-max/v1
+  - context: gitea-ssh/v1
+  - context: agent-repo/v1

harnesses/composites/scaffolding-repo/v1/harness.yaml

@@ -5,6 +5,9 @@ description: "Model-agnostic scaffolding harness — writes stubs for coding age
 
 layers:
   - context: scaffolding/v1
-  - context: anthropic-cloud-paul-oauth/v1
+  # MiniMax M3 — scaffolding is mechanical (stub files so tests import);
+  # moved off the personal Anthropic subscription 2026-09-02.
+  - context: minimax/v1
+  - context: minimax-m3-max/v1
   - context: gitea-ssh/v1
   - context: agent-repo/v1

harnesses/composites/spec-writing-fable-low-repo/v1/harness.yaml

@@ -0,0 +1,11 @@
+kind: composite
+name: spec-writing-fable-low-repo
+version: 1
+description: "Spec writing agent on Fable 5 (low effort) + repo clone via SSH"
+
+layers:
+  - context: spec-writing/v1
+  - context: anthropic-cloud-paul-oauth/v1
+  - context: fable-low-effort/v1
+  - context: gitea-ssh/v1
+  - context: agent-repo/v1

harnesses/composites/test-writing-repo/v1/harness.yaml

@@ -5,6 +5,10 @@ description: "Model-agnostic test writing harness — credential layer swappable
 
 layers:
   - context: test-writing/v1
-  - context: anthropic-cloud-paul-oauth/v1
+  # MiniMax M3 max effort — moved off the personal Anthropic subscription
+  # 2026-09-02 (the "credential layer swappable" swap this composite was
+  # designed for).
+  - context: minimax/v1
+  - context: minimax-m3-max/v1
   - context: gitea-ssh/v1
   - context: agent-repo/v1