fix(browser): stop waiting for full page load - #1539

Summary

• consider the initial Browser IdP navigation complete when the response is committed
• avoid aborting authentication when an IdP page does not fire the full load event within Playwright's 30-second navigation timeout
• add a focused unit test for the navigation wait condition

Rationale

The Browser provider only needs the IdP document to start loading before it can wait for the SAML POST to AWS. Waiting for every page resource to finish is unnecessary and can close an otherwise usable login page before the user can authenticate. The commit state still verifies that navigation received a response while allowing the existing SAML request listener to continue waiting.

Testing

• go test ./pkg/provider/browser -run 'TestNavigateToLoginPageWaitsForCommit|TestSigninRegex|TestExpectRequestOptions' -count=1
• go test ./cmd/saml2aws/commands -count=1
• go vet ./pkg/provider/browser
• built from the current master branch and completed an end-to-end Browser provider SAML login that previously failed with Frame.Goto ... Timeout 30000ms exceeded