refactor: extract planner and coder into standalone role packages

- New @uncaged/workflow-role-planner (phaseSchema, createPlannerRole)
- New @uncaged/workflow-role-coder (coderMetaSchema, createCoderRole)
- solve-issue template imports from new packages, keeps dry-run defaults

小橘 <xiaoju@shazhou.work>

packages/workflow-role-coder/package.json

@@ -0,0 +1,17 @@
+{
+  "name": "@uncaged/workflow-role-coder",
+  "version": "0.1.0",
+  "type": "module",
+  "main": "src/index.ts",
+  "types": "src/index.ts",
+  "scripts": {
+    "build": "echo 'TODO'",
+    "test": "bun test"
+  },
+  "dependencies": {
+    "@uncaged/workflow": "workspace:*",
+    "@uncaged/workflow-agent-llm": "workspace:*",
+    "@uncaged/workflow-util-role": "workspace:*",
+    "zod": "^4.0.0"
+  }
+}