chore(harness): isolate pi stage execution

harness/contracts/handoff.md

@@ -5,6 +5,14 @@ Los agentes **no** devuelven código en chat. Deben escribir a disco y responder
 - `done -> <ruta>`
 - `blocked -> <ruta>`
 
+## Contexto mínimo por stage
+Cada stage recibe solo:
+1. Los archivos listados en `harness/workflow.stages.yml` como `input`.
+2. El artefacto del stage anterior cuando el workflow lo declare.
+3. La memoria Engram que el leader seleccione explícitamente para ese stage.
+
+No se considera válido pasar todo el chat anterior como contexto operativo. Si un stage necesita más información, debe pedir una ruta o artefacto concreto y bloquear hasta tenerlo.
+
 ## Rutas estándar por feature
 - `work/artifacts/<feature_id>/implementer.md`
 - `work/artifacts/<feature_id>/reviewer.json`

harness/workflow.stages.yml

@@ -15,29 +15,54 @@ stages:
   - name: design
     owner: architect
     optional: true
+    input:
+      - work/current.md
+      - spec/product.md
+      - spec/tech.md
+      - spec/acceptance.md
     output:
       - work/artifacts/<feature_id>/architect.md
 
   - name: build
     owner: implementer
+    input:
+      - work/current.md
+      - spec/product.md
+      - spec/tech.md
+      - spec/acceptance.md
+      - work/artifacts/<feature_id>/architect.md
     output:
       - work/artifacts/<feature_id>/implementer.md
 
   - name: review_gate
     owner: reviewer
     required: true
+    input:
+      - work/current.md
+      - spec/acceptance.md
+      - work/artifacts/<feature_id>/implementer.md
     output:
       - work/artifacts/<feature_id>/reviewer.json
 
   - name: security_gate
     owner: security
     required: true
+    input:
+      - work/current.md
+      - work/artifacts/<feature_id>/implementer.md
+      - work/artifacts/<feature_id>/reviewer.json
     output:
       - work/artifacts/<feature_id>/security.json
 
   - name: qa_gate
     owner: qa
     required: true
+    input:
+      - work/current.md
+      - spec/acceptance.md
+      - work/artifacts/<feature_id>/implementer.md
+      - work/artifacts/<feature_id>/reviewer.json
+      - work/artifacts/<feature_id>/security.json
     output:
       - work/artifacts/<feature_id>/qa.json
 
@@ -45,12 +70,25 @@ stages:
     owner: documenter
     optional: true
     when: docs/API/contracts/user-facing behavior changed
+    input:
+      - work/current.md
+      - work/artifacts/<feature_id>/implementer.md
+      - work/artifacts/<feature_id>/reviewer.json
+      - work/artifacts/<feature_id>/security.json
+      - work/artifacts/<feature_id>/qa.json
     output:
       - work/artifacts/<feature_id>/documenter.md
 
   - name: close
     owner: leader
     required: true
+    input:
+      - work/current.md
+      - work/artifacts/<feature_id>/implementer.md
+      - work/artifacts/<feature_id>/reviewer.json
+      - work/artifacts/<feature_id>/security.json
+      - work/artifacts/<feature_id>/qa.json
+      - work/artifacts/<feature_id>/documenter.md
     output:
       - work/artifacts/<feature_id>/leader-close.json
       - work/history.md