Optimize the Select Syntax Scheme dialog

[liangjiancang]

When "Auto-select by filename extension" is checked, the best Scheme detected should be displayed at the first or third position (after "2nd Common Base").

In the current version, if user temporarily switch to "Common Base", then switching back to the "correct" scheme requires user finding the correct one in a very long list.

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For example, with an .html file:

current:

expected:

[RaiKoHoff]

Focus and Highlight current Lexer Syntax Scheme is good enough (close and re-open by double-click does the job).

[liangjiancang]

I disagree that “focus and highlight is good enough.”

• Efficiency: With auto‑selection on, after temporarily switching to another scheme, the user still has to scan a long list to find the correct one—highlighting alone doesn’t help with that.
• Expectation: Auto‑selection should place the best match at a prominent position (top or after “2nd Common Base”), not just mark it somewhere in the list.
• Workaround ≠ solution: “Close and re‑open” only works if the user wants to keep the current scheme; the problem is when they want to revert while the dialog is still open.
• Low cost, high benefit: The best scheme is already known; moving it to a fixed spot is a small change with clear usability gain.

I think this improvement is worth implementing.