Bug Description

When creating a new session, ACP correctly merges user-provided hooks and mcpServers from _meta.claudeCode.options with its own internal values. However, disallowedTools is overwritten rather than merged.

Root Cause

In src/acp-agent.ts, user-provided options are spread at line 1000:

...userProvidedOptions,

But then ACP's internal disallowedTools unconditionally overwrites the user's value at line 1108:

options.disallowedTools = disallowedTools;

Any disallowedTools passed via _meta.claudeCode.options are silently lost.

Expected Behavior

disallowedTools should be merged with user-provided values, matching the established pattern used for hooks (lines 1017-1047) and mcpServers (line 1004):

// mcpServers merge pattern (line 1004):
mcpServers: { ...(userProvidedOptions?.mcpServers || {}), ...mcpServers },

// hooks merge pattern (lines 1017-1047):
hooks: {
  ...userProvidedOptions?.hooks,
  PreToolUse: [
    ...(userProvidedOptions?.hooks?.PreToolUse || []),
    // ...ACP's hooks
  ],
  // ...
}

Proposed Fix

// Before:
options.disallowedTools = disallowedTools;

// After:
options.disallowedTools = [...(userProvidedOptions?.disallowedTools || []), ...disallowedTools];

The NewSessionMeta JSDoc should also be updated to document that disallowedTools is merged (like hooks and mcpServers).