fix(workbench): positron extensions test looks for wrong element selector

Problem

test_positron_extensions[chromium] fails looking for get_by_role("button", name="home Posit Workbench") but the actual Positron UI has a tab element named "Posit Workbench" instead.

Observed at: PHS UAT (pwb-uat.publichealthscotland.org) on 2026-05-20

Error output:

Locator expected to be visible
waiting for get_by_role("button", name="home Posit Workbench")

The accessibility tree dump shows Positron loaded successfully with a tab labeled "Posit Workbench" visible in the sidebar:

- tab "Posit Workbench"

The step "the Posit Workbench extension is visible in Positron" (test_ide_extensions.py:280-287) waits for a button with name "home Posit Workbench", but newer Positron versions appear to render this as a tab in the Activity Bar rather than a button.

Expected Behavior

The selector should match the actual UI element that represents the Posit Workbench extension presence — whether it's rendered as a button or a tab.

Suggested Fix

Update the selector to look for the Posit Workbench extension indicator using a more resilient locator, e.g.:

• page.get_by_role("tab", name="Posit Workbench") or
• A locator that accepts either role

Reproduction

Run VIP against a Workbench instance with a recent Positron version installed.

Start in test_ide_extensions.py:280-287, where the Posit Workbench extension visibility step uses the button locator. Check the accessibility tree in a Workbench instance with a recent Positron version, then update the selector to match the rendered extension indicator. Done means test_positron_extensions[chromium] passes when the indicator is a tab or button.