Move the Orbit query editor into its own tab

What does this MR do and why?

Moves the Orbit query editor from a panel on Explore to its own Query editor tab, with schema suggestions, a query reference drawer, examples, and Ask Duo. No feature flag: it uses the same APIs as the old panel. With the GQL flag off, the editor takes JSON.

Closes gitlab-org/orbit/knowledge-graph#1365 (closed)

Screenshots or screen recordings

Before	After

Happy path	Bad path	Disaster path

More recordings and screenshots

View	Recording or screenshot
Query reference
JSON mode
JSON examples
Review fixes
Before
Suggestions
Error
No Orbit access
390
Dark

How to set up and validate locally

Go to /dashboard/orbit/query, press Tab, then Cmd+Enter.

MR acceptance checklist

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