feat(core,cli)!: Implement in-process agent backend for arenas

Co-authored-by: Qwen-Coder <qwen-coder@alibabacloud.com>

Add InProcessBackend to run subagents in-process rather than via subprocess,

enabling faster initialization and better resource management for agent

collaboration arenas.

Key changes:

- Add InProcessBackend with sandboxed in-process agent execution

- Refactor agent runtime into headless vs interactive modes

- Add AsyncMessageQueue utility for agent message passing

- Update ArenaManager with backend selection (in-process vs subprocess)

- Refactor subagent types/exports; consolidate in subagents/types

- Remove deprecated agent-hooks.ts (functionality merged into runtime)

- Update task tool to support new agent lifecycle

Breaking: Subagent type exports restructured; import from subagents/types

packages/cli/src/config/settingsSchema.ts

@@ -1231,6 +1231,26 @@ const SETTINGS_SCHEMA = {
               'When enabled, Arena worktrees and session state files are preserved after the session ends or the main agent exits.',
             showInDialog: true,
           },
+          maxRoundsPerAgent: {
+            type: 'number',
+            label: 'Max Rounds Per Agent',
+            category: 'Advanced',
+            requiresRestart: false,
+            default: undefined as number | undefined,
+            description:
+              'Maximum number of rounds (turns) each agent can execute. No limit if unset.',
+            showInDialog: false,
+          },
+          timeoutSeconds: {
+            type: 'number',
+            label: 'Timeout (seconds)',
+            category: 'Advanced',
+            requiresRestart: false,
+            default: undefined as number | undefined,
+            description:
+              'Total timeout in seconds for the Arena session. No limit if unset.',
+            showInDialog: false,
+          },
         },
       },
       team: {