Add waitForReady support to BasePageObject

[Zachary Artman (zacharyartman)]

Overview of Changes

• BasePageObject gains a protected waitForReady() hook, a no-op by default. createFromPage and both forms of create now await it before returning the new page object, so a navigation method like openContractors returns a page that is ready to use. Pass { waitForReady: false } to either to skip the wait.

Checklist

• Changes follow the code style of this project
• Self-review completed
• Tests added/updated (or not applicable)
• No breaking changes (or described below)

Breaking Change: Callers that use createFromPage's result without awaiting must add an await.