Is the company liable for post-traumatic OA dominant right wrist mild carpal tunnel?

You will need to file a workman's comp claim. They have schedules that define the payout for such an injury.

If the repetitive stress injury was job related then State Industrial Insurance should cover it depending upon when the problem was discovered and when, and if, you turned it in to L & I. Contact an attorney specializing in Industrial Insurance matters.,

The employer is not liable. You have injuries covered under the WA workers compensation program and if your doctor agrees that your injuries are work related the doctor can fill out a workers comp claim form which is provide medical bill benefits, time loss ( like unemployment benefits) and if you have a permanent partial disability condition, the benefits include a lump sum payment.