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/db.ts

@@ -600,7 +600,7 @@ export function getRegisteredGroup(
     folder: row.folder,
     trigger: row.trigger_pattern,
     added_at: row.added_at,
-    containerConfig: row.container_config
+    agentConfig: row.container_config
       ? JSON.parse(row.container_config)
       : undefined,
     requiresTrigger:
@@ -624,7 +624,7 @@ export function setRegisteredGroup(jid: string, group: RegisteredGroup): void {
     group.folder,
     group.trigger,
     group.added_at,
-    group.containerConfig ? JSON.stringify(group.containerConfig) : null,
+    group.agentConfig ? JSON.stringify(group.agentConfig) : null,
     group.requiresTrigger === undefined ? 1 : group.requiresTrigger ? 1 : 0,
     group.isMain ? 1 : 0,
     group.agentType || 'claude-code',
@@ -659,7 +659,7 @@ export function getAllRegisteredGroups(): Record<string, RegisteredGroup> {
       folder: row.folder,
       trigger: row.trigger_pattern,
       added_at: row.added_at,
-      containerConfig: row.container_config
+      agentConfig: row.container_config
         ? JSON.parse(row.container_config)
         : undefined,
       requiresTrigger: