revert: add full file when selection is empty

[uinstinct]

Description

Reverts #6711

Do not add the full file when selection is empty. Only focus on the extension editor.

resolves CON-4936

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• [] The relevant docs, if any, have been updated or created
• [] The relevant tests, if any, have been updated or created

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Summary by cubic

Reverts the change that added the full file when no text is selected. The extension now only adds the highlighted selection to context and skips related E2E tests, addressing CON-4936.

^{Written for commit 1bf2385. Summary will update automatically on new commits.}

[cubic-dev-ai]

No issues found across 1 file

[RomneyDa]

@uinstinct looks like there are tests for this functionality which will need to be updated.

Also could we change the language from "reverts" to "related" or "reverts some behavior"? It's not a full reversion as that PR also added other thing like removing sidebar toggle etc.

CON-4936 also involves fixing CMD + Shift + L. Could we address that issue here as well?

[RomneyDa]

Thanks for the updates!