Scope runtime diagnostics to dashboard on 1.7.0 beta

[mehul0810]

Summary

• scope the full Runtime Diagnostics panel to the Dashboard tab only
• keep the dashboard diagnostics visible while removing the panel from non-dashboard tabs
• update the smoke test so General no longer expects the diagnostics panel

Issue

• closes Scope Runtime Diagnostics to the Dashboard tab on the 1.7.0 beta settings UI #169

Validation

• npm run lint:js
• composer test
• npm run build

Proof gap

• Before and after screenshots are still blocked in this automation path.
• studio wp succeeds, but external browser automation against https://development.wp.local/ is returning a Studio runtime / Internal Server Error body instead of a usable settings page, so the requested visual proof could not be attached from the CLI path in this turn.
• The blocker issue records that gap explicitly and this PR should not be treated as fully release-ready until after screenshots are attached or the Studio/browser path is repaired.

[github-actions]

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