feat: improve Wiki decoration E2E with collab and close-confirm helpers

[NishikawaKoharu]

Purpose

Improve Wiki operation E2E tests by adding Playwright helpers for collaborative editing and close-confirmation flows, and updating WikiDecoration.ipynb to use them.

Wiki decoration tests were unstable in collaborative editing mode, and close-confirmation / live-sync scenarios needed dedicated automation support. This PR adds helpers to scripts/grdm.py and updates test steps in WikiDecoration.ipynb so these scenarios can run in E2E tests.

Changes

• Add Wiki navigation, collaborative editing, text input, and dialog assertion helpers to scripts/grdm.py
• Add open_edit_wiki_collab without changing existing open_edit_wiki behavior
• Update WikiDecoration.ipynb to run decoration tests in collaborative editing mode
• Add close-confirmation test steps to WikiDecoration.ipynb (unsaved Close, discard, save, beforeunload, etc.)
• Fix the live-sync step after Close (peer handoff, live append, and re-edit on the receiver tab)

Ticket

https://redmine.devops.rcos.nii.ac.jp/issues/62163

Custom Test Configuration

• RDM_REPOSITORY:
• RDM_BRANCH:
• RDM_MERGE:

• OSF_IMAGE:
• EMBER_IMAGE:
• CAS_IMAGE:
• MFR_IMAGE:
• WB_IMAGE:
• EXCLUDE_NOTEBOOKS: