Spike: PTY-based Claude Code integration with multi-agent concurrency

Proves that spawning `claude -p` in a pseudo-terminal from Rust gets Max
subscription billing (apiKeySource: "none", rateLimitType: "five_hour")
instead of per-token API charges. Concurrent agents run in parallel PTY
sessions with session resumption via --resume for multi-turn conversations.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

server/src/http/context.rs

@@ -1,3 +1,4 @@
+use crate::agents::AgentPool;
 use crate::state::SessionState;
 use crate::store::JsonFileStore;
 use crate::workflow::WorkflowState;
@@ -9,6 +10,7 @@ pub struct AppContext {
     pub state: Arc<SessionState>,
     pub store: Arc<JsonFileStore>,
     pub workflow: Arc<std::sync::Mutex<WorkflowState>>,
+    pub agents: Arc<AgentPool>,
 }
 
 pub type OpenApiResult<T> = poem::Result<T>;