fix(agent-management): pass env vars to agent in spawn_streaming

The spawn_streaming() function was not passing environment variables
from SpawnOptions.env to the spawned process. This caused agents like
Claude to not receive ANTHROPIC_API_KEY, resulting in silent
authentication failures.

The non-streaming spawn() method correctly passes env vars (lines 298-300),
but spawn_streaming() was missing this code path.

This fix adds the same env var loop to spawn_streaming(), ensuring that
credentials extracted from the host environment are properly passed to
spawned agents.

server/packages/agent-management/src/agents.rs

@@ -327,6 +327,12 @@ impl AgentManager {
             options.streaming_input = true;
         }
         let mut command = self.build_command(agent, &options)?;
+
+        // Pass environment variables to the agent process (e.g., ANTHROPIC_API_KEY)
+        for (key, value) in &options.env {
+            command.env(key, value);
+        }
+
         if matches!(agent, AgentId::Codex | AgentId::Claude) {
             command.stdin(Stdio::piped());
         }