refactor: all-agentic architecture — roles as pure data, agent binding at runtime

BREAKING: Major architecture change.

- RoleDefinition = pure data (systemPrompt + schema + dryRunMeta)
- AgentFn = (ctx: ThreadContext) => Promise<string>, reads ctx.currentRole
- WorkflowDefinition decoupled from agents, bound via AgentBinding at runtime
- createWorkflow(def, binding, extract) replaces createRoleModerator
- Meta extraction moved into engine loop
- Delete workflow-util-role package (createRole, decorators, extract all gone)
- Role packages become pure data exports
- Agent packages updated to single-arg AgentFn

小橘 <xiaoju@shazhou.work>

tsconfig.json

@@ -18,7 +18,6 @@
   },
   "references": [
     { "path": "packages/workflow" },
-    { "path": "packages/workflow-util-role" },
     { "path": "packages/workflow-agent-llm" },
     { "path": "packages/workflow-role-committer" },
     { "path": "packages/workflow-role-coder" },