outline: Switch the outline search to use fuzzy_nucleo

[feitreim]

Nucleo tracking issue: #55872

This PR switches the outline picker to use fuzzy_nucleo.

with that I refactored the outline fuzzy picking to take advantage of nucleo and its multi-atom query support. The previous implementation had a lot going on specifically to work around the lack of multiple atoms, basically taking matters into its own hands to accomplish the same goals within the constraints it had.

Instead of having two lists of candidates that we have to run the query against, we just run a single query and take advantage of the fact that nucleo chooses the matches that are the furtherest towards the end of the haystack to implement the same ancestor/leaf filtering. It retains the leaf only matching on single atom queries.

video:

Screen.Recording.2026-05-11.at.4.50.19.PM.mov

Self-Review Checklist:

• I've reviewed my own diff for quality, security, and reliability
• Unsafe blocks (if any) have justifying comments
• The content is consistent with the UI/UX checklist
• Tests cover the new/changed behavior
• Performance impact has been considered and is acceptable

Release Notes:

• outline: switch to fuzzy_nucleo

[zed-industries-bot]

	Messages
📖	This PR includes links to the following GitHub Issues: #55872 If this PR aims to close an issue, please include a Closes #ISSUE line at the top of the PR body.

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[yara-blue]

I was out for a week and it has taken a bit to catch up with everything, apologies.
I really appreciate you putting all this effort into fuzzy search!!

Now on to the review, I'm struggling a little in fully understanding all the needed changes. I've left some comments explaining my confusion, do you see a way to rework this (renames/comments) to make it easier to read? I'm not saying it is bad code! I'm saying search is hard, especially when trees get involved :)

[feitreim]

Okay so I fixed the typo and the unused dependency thing. but the clippy failure/test failure case

error[E0308]: mismatched types
   --> crates/language/src/outline.rs:319:19
    |
319 |             text: "completion".to_string(),
    |                   ^^^^^^^^^^^^^^^^^^^^^^^^ expected `SharedString`, found `String`
    |
help: call `Into::into` on this expression to convert `std::string::String` into `gpui::SharedString`
    |
319 |             text: "completion".to_string().into(),
    |                                           +++++++

straight up does not exist. the line where I have something very similar happening, I already use .into(). so uh, hopefully that goes away?

[yara-blue]

straight up does not exist. the line where I have something very similar happening, I already use .into(). so uh, hopefully that goes away?

we'll see :)

[yara-blue]

yeah this is kinda crazy, lets see if I get this locally