fix: add missing 'question' tool to ToolAccessSchema (#269)

The 'question' tool is a built-in OpenCode tool used to ask users
to make decisions, but it was missing from the ToolAccessSchema in
types.ts and the isValidOACTool() function in ToolMapper.ts.

This prevented OpenCoder/OpenAgent agents from accessing the tool
even when explicitly configured.

Changes:
- Add question: z.boolean().optional() to ToolAccessSchema
- Add 'question' to validTools array in isValidOACTool()

Fixes #268

Co-authored-by: BillionClaw <267901332+BillionClaw@users.noreply.github.com>