refactor: rename container references to agent across codebase

- container-runner.ts → agent-runner.ts
- ContainerInput/Output → AgentInput/Output
- ContainerConfig → AgentConfig
- runContainerAgent → runAgentProcess
- CONTAINER_TIMEOUT → AGENT_TIMEOUT (with env fallback)
- MAX_CONCURRENT_CONTAINERS → MAX_CONCURRENT_AGENTS
- containerName → processName, isTaskContainer → isTaskProcess
- DB column container_config kept as-is (backwards compat)

src/session-commands.ts

@@ -26,7 +26,7 @@ export function isSessionCommandAllowed(
   return isMainGroup || isFromMe;
 }
 
-/** Minimal agent result interface — matches the subset of ContainerOutput used here. */
+/** Minimal agent result interface — matches the subset of AgentOutput used here. */
 export interface AgentResult {
   status: 'success' | 'error';
   result?: string | object | null;