Add role-local migrated skill guidance

packages/codebase-design/SKILL.md

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+---
+name: codebase-design
+description: Examine module interfaces and seams while drafting a repository Plan.
+metadata:
+  relayview-display-name: Codebase design
+  relayview-version: 0.3.0
+---
+
+# Codebase design for Planner
+
+Use this guidance while deciding the implementation boundary of an assigned Plan. Read the repository's current architecture, relevant code and tests before proposing a module change. Use the [module guide](module-guide.md) to compare interfaces and identify the smallest seam that can carry the requested behavior.
+
+Describe the existing interface, the behavior hidden behind it, and the caller obligations that a change would add or remove. Compare at least two plausible designs in the Plan when the seam is consequential. Record a recommendation with the trade-off and a testable observation, rather than treating a preferred abstraction as verified behavior.
+
+Submit the result through the assigned planning interface. Keep code edits, branch operations, subagent scheduling, and workflow transitions with their existing owner-controlled roles and stages.

packages/codebase-design/module-guide.md

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+# Module guide
+
+- A module is a unit with an interface and an implementation; its interface includes invariants, ordering, errors, configuration, and performance obligations as well as types.
+- Prefer depth: useful behavior behind a small interface. Assess what callers must learn and where future changes will concentrate.
+- A seam is where the interface lives. Name the dependency that varies there and the concrete adapters that justify it; do not add a speculative port for one fixed implementation.
+- Test proposed behavior through the interface visible to callers. Identify the existing tests that would stay meaningful after an internal refactor.
+- Classify dependencies as in-process, locally substitutable, owned remote, or external before recommending an adapter or verification seam.
+- State what each candidate hides, what it exposes, and how an implementer can prove the selected behavior. A diagram or example may clarify a design, but it is not verification evidence.

packages/codebase-design/relayview-skill.json

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+{
+  "schemaVersion": 1,
+  "source": {
+    "kind": "first-party",
+    "reference": "v0.3.0"
+  },
+  "role": "planner",
+  "step": "planning",
+  "files": [
+    {
+      "path": "SKILL.md",
+      "sha256": "8633b139187c3ba62e75338f3792ef6d7a445559b792cfb4926cb722609c161a"
+    },
+    {
+      "path": "module-guide.md",
+      "sha256": "7bb0fa0d1a54dce4469e0ceedade86e2efe1e4cd11cac6f1276ed7fb6dca06f5"
+    }
+  ]
+}