refactor: replace UWF_EDGE_PROMPT env var with named CLI args

Agent adapters now use named parameters:
  uwf-<agent> --thread <id> --role <role> --prompt <text>

Instead of positional args + env var:
  UWF_EDGE_PROMPT=... uwf-<agent> <thread-id> <role>

Changes:
- workflow-agent-kit/src/run.ts: parseArgv uses named --thread/--role/--prompt
- workflow-agent-kit/src/context.ts: edgePrompt passed as parameter, not read from env
- cli-workflow/src/commands/thread.ts: spawnAgent passes named args

小橘 <xiaoju@shazhou.work>

packages/cli-workflow/src/commands/thread.ts

@@ -804,13 +804,11 @@ function spawnAgent(
   role: string,
   edgePrompt: string,
 ): CasRef {
-  const argv = [...agent.args, threadId, role];
-  const env = { ...process.env, UWF_EDGE_PROMPT: edgePrompt };
+  const argv = [...agent.args, "--thread", threadId, "--role", role, "--prompt", edgePrompt];
   let stdout: string;
   try {
     stdout = execFileSync(agent.command, argv, {
       encoding: "utf8",
-      env,
       stdio: ["ignore", "pipe", "pipe"],
       maxBuffer: 50 * 1024 * 1024, // 50 MB — stream-json output can be large
     });