Add completion_query_characters in language (#27175)

Closes #18581

Now characters for completing query and word characters, which are
responsible for selecting words by double clicking or navigating, are
different. This fixes a bunch of things:

For settings.json, this improves completions to treat the whole string
as a completion query, instead of just the last word. We now added
"space" as a completion query character without it being a word
character.

For keymap.json, this improves selecting part of an action as the ":"
character is only a completion character and not a word character. So,
completions would still trigger on ":" and query capture will treat ":"
as a word, but for actions like selections and navigation, ":" will be
treated as punctuation.

Before:
Unnecessary related suggestions as query is only the last word which is
"d".
<img width="300" alt="image"
src="https://github.com/user-attachments/assets/8199a715-7521-49dd-948b-e6aaed04c488"
/>

Double clicking `ToggleFold` selects the whole action:
<img width="300" alt="image"
src="https://github.com/user-attachments/assets/c7f91a6b-06d5-45b6-9d59-61a1b2deda71"
/>

After:
Now query is "one d" and it shows only matched ones.
<img width="300" alt="image"
src="https://github.com/user-attachments/assets/1455dfbc-9906-42e8-b8aa-b3f551194ca2"
/>

Double clicking `ToggleFold` only selects part of the action, which is
more refined behavior.
<img width="300" alt="image"
src="https://github.com/user-attachments/assets/34b1c3c2-184f-402f-9dc8-73030a8c370f"
/>

Release Notes:

- Improved autocomplete suggestions in `settings.json`, now whole string
is queried instead of just last word of string, which filters out lot of
false positives.
- Improved selection of action in `keymap.json`, where now you can
double click to only select certain part of action, instead of selecting
whole action.

---------

Co-authored-by: Max Brunsfeld <maxbrunsfeld@gmail.com>
Co-authored-by: Ben Kunkle <ben@zed.dev>

docs/src/extensions/languages.md

@@ -223,7 +223,9 @@ Note that we couldn't use JSON as an example here because it doesn't support lan
 
 The `overrides.scm` file defines syntactic _scopes_ that can be used to override certain editor settings within specific language constructs.
 
-For example, there is a language-specific setting called `word_characters` that controls which non-alphabetic characters are considered part of a word, for filtering autocomplete suggestions. In JavaScript, "$" and "#" are considered word characters. But when your cursor is within a _string_ in JavaScript, "-" is _also_ considered a word character. To achieve this, the JavaScript `overrides.scm` file contains the following pattern:
+For example, there is a language-specific setting called `word_characters` that controls which non-alphabetic characters are considered part of a word, for example when you double click to select a variable. In JavaScript, "$" and "#" are considered word characters.
+
+There is also a language-specific setting called `completion_query_characters` that controls which characters trigger autocomplete suggestions. In JavaScript, when your cursor is within a _string_, "-" is should be considered a completion query character. To achieve this, the JavaScript `overrides.scm` file contains the following pattern:
 
 ```scheme
 [
@@ -238,7 +240,7 @@ And the JavaScript `config.toml` contains this setting:
 word_characters = ["#", "$"]
 
 [overrides.string]
-word_characters = ["-"]
+completion_query_characters = ["-"]
 ```
 
 You can also disable certain auto-closing brackets in a specific scope. For example, to prevent auto-closing `'` within strings, you could put the following in the JavaScript `config.toml`: