prompt-buffer: urgent fixes

[Ambrevar]

1. switch-buffer loses focus because follow-mode is on.
   We need to maintain focus on the input when following buffer.

2. The bookmark-url related commands should pre-mark the tags of existing bookmarks (easy).

3. (Not actually urgent) Element-hinting functions need a custom filter to match against the hints.

4. Re-introduce tab-insert, especially for set-url.

[Ambrevar]

@jmercouris Indeed, I cannot reproduce "3". I think the issue occurs when a title has the same word as a hint, e.g. at. The hint-source does not take any provision to match hint first, so I guess there is still an issue, but it's no longer urgent since it works most of the time.

[jmercouris]

I would say that is a likely explanation, yes.

[Ambrevar]

I've fixed the missing tab-insert.

For bookmark pre-marks, I've implemented it but it seems to work only rarely.
Any idea why?

[jmercouris]

What are bookmark "pre-marks"?

[jmercouris]

Do you mean pre-marked tags within the prompt buffer? Are they marked by not rendering as marked? Could it be that we need to run an update-display event after some processing?

[Ambrevar]

Do you mean pre-marked tags within the prompt buffer?

Yes.

Are they marked by not rendering as marked? Could it be that we need to run an update-display event after some processing?

I don't think that's the problem, because upon inspecting I see that if I mark "foo" which is already premarked, the marks value is '("foo" "foo"). It's as if the test function didn't work. Am I using `eq` instead of `equal`? I'll check tomorrow.

[Ambrevar]

Fixed with 9d1b48d.
Moving the optional item to atlas-engineer/prompter#32.