feat: add v2 task control and asynchronous isolated workers

include/cst_agent.h

@@ -112,14 +112,17 @@ typedef struct {
   /* Sub-agents (task tool). */
   int depth;              /* 0 = top-level; sub-agents run at 1 */
   int orchestrate;        /* coordinator delegates write/shell work */
+  struct cst_runtime *runtime; /* V2 task controller; parent-owned */
   int orchestrate_override; /* CLI: 1 force on, -1 force off */
   int subagent_steps, subagent_tasks, subagent_total;
   void *worker_budget;    /* owned by the top-level agent */
   int (*request_gate)(void *); /* reserve budget before each HTTP attempt */
   void *request_gate_ud;
+  unsigned long task_revision;
   char cache_namespace[128];
   int read_only;          /* no write / shell tools */
   char tools_only[1024];  /* ",a,b," allowlist; empty = every tool */
+  char worker_scope[2048]; /* isolated worker's JSON path allowlist */
   const char *role_prompt; /* role instructions (not owned) */
   char undo_sid[128];     /* snapshot into this session's undo... */
   char undo_tag[64];      /* ...under this turn tag (the parent's) */
@@ -387,6 +390,8 @@ cst_session_t *cst_agent_session(cst_agent_t *a);
 const cst_agent_config_t *cst_agent_config(const cst_agent_t *a);
 cst_agent_config_t *cst_agent_config_mut(cst_agent_t *a);
 void cst_agent_request_cancel(cst_agent_t *a);
+int cst_agent_steer(cst_agent_t *a, const char *message, int readonly, int delegation);
+int cst_agent_control(cst_agent_t *a, int readonly, int delegation, int paused);
 int cst_agent_new_session(cst_agent_t *a, char *id_out, size_t id_sz);
 int cst_agent_switch_session(cst_agent_t *a, const char *id);
 /* Re-root the agent at another directory. Per-workspace state (permission