refactor(agents): migrate LLM/Hermes/Cursor to createAgentAdapter

- LLM: AgentFn<{prompt}> + createAgentAdapter, chatCompletionText unchanged
- Hermes: AgentFn<{prompt}> + createAgentAdapter, config validation in extract
- Cursor: AgentFn<{prompt, workspace}> + createAgentAdapter, workspace
  extraction moved to extract fn, AgentFn itself only receives resolved options

All public API signatures preserved. createTextAdapter/TextProducerFn retained.

Closes #261, Phase 2 of #252

develop-entry.ts

@@ -9,6 +9,7 @@ const agent = createCursorAgent({
   command: "/home/azureuser/.local/bin/cursor-agent",
   model: "auto",
   timeout: 300_000,
+  workspace: null,
 });
 
 export const descriptor = buildDevelopDescriptor();