feat!: align standard captures with upstream

Problem: Sharing highlight queries with upstream tree-sitter and
Helix is difficult.

Solution: Where reasonable, use capture names in tree-sitter's standard
list or Helix's Atom-style hierarchy.

Specifically:

* tree-sitter "standard capture names"
  (3f44b89685/highlight/src/lib.rs (L20-L72)):

  - `@parameter` -> `@variable.parameter`
  - `@field` -> `@variable.member`
  - `@namespace` -> `@module`
  - `@float` -> `@number.float`
  - `@symbol` -> `@string.special.symbol`
  - `@string.regex` -> `@string.regexp`
  - `@text.*` -> `@markup.*` (`strong`, `italic`, `link`, `strikethrough`; with exceptions; see below)
  - `@text.title` -> `@markup.heading`
  - `@text.literal` -> `@markup.raw`
  - `@text.reference` -> `@markup.link`
  - `@text.uri` -> `@markup.link.url` (in markup links)
  - `@string.special` -> `@markup.link.label` (non-url links)
  - `@punctuation.special` -> `@markup.list` (markdown lists only; move subitems from `@text.todo`)

* Helix captures
  (https://docs.helix-editor.com/master/themes.html#syntax-highlighting):

  - `@method` -> `@function.method`
  - `@method.call` -> `@function.method.call`
  - `@text.{todo,warning,note,danger}` -> `@comment.{error,warning,hint,info,todo}`
  - `@text.diff.{add,delete,}` -> `@diff.{plus,minus,delta}`
  - `@text.uri` -> `@string.special.url` (outside markup)
  - `@preproc` -> `@keyword.directive`
  - `@define` -> `@keyword.directive`(`.define`?)
  - `@storageclass` -> `@keyword.storage`
  - `@conditional` -> `@keyword.conditional`
  - `@debug` -> `@keyword.debug`
  - `@exception` -> `@keyword.exception`
  - `@include` -> `@keyword.import`
  - `@repeat` -> `@keyword.repeat`

* cleanup

  - remove some redundant `@conceal` (but still allow it for conceal-only patterns)
  - remove obsolete `@error` (syntax linting is out of scope for this repo)
  - sort, cleanup capture list in `CONTRIBUTING.md`

queries/ruby/highlights.scm

@@ -45,10 +45,10 @@
  "unless"
  "when"
  "then"
- ] @conditional
+ ] @keyword.conditional
 
 (if
-  "end" @conditional)
+  "end" @keyword.conditional)
 
 [
  "for"
@@ -58,7 +58,7 @@
  "redo"
  "retry"
  "next"
- ] @repeat
+ ] @keyword.repeat
 
 (constant) @constant
 
@@ -68,10 +68,10 @@
 [
  "rescue"
  "ensure"
- ] @exception
+ ] @keyword.exception
 
-((identifier) @exception
- (#any-of? @exception "fail" "raise"))
+((identifier) @keyword.exception
+ (#any-of? @keyword.exception "fail" "raise"))
 
 ; Function calls
 
@@ -87,8 +87,8 @@
 
 (program
  (call
-  (identifier) @include)
- (#any-of? @include "require" "require_relative" "load"))
+  (identifier) @keyword.import)
+ (#any-of? @keyword.import "require" "require_relative" "load"))
 
 ; Function definitions
 
@@ -126,15 +126,15 @@
  (super)
  ] @variable.builtin
 
-(method_parameters (identifier) @parameter)
-(lambda_parameters (identifier) @parameter)
-(block_parameters (identifier) @parameter)
-(splat_parameter (identifier) @parameter)
-(hash_splat_parameter (identifier) @parameter)
-(optional_parameter (identifier) @parameter)
-(destructured_parameter (identifier) @parameter)
-(block_parameter (identifier) @parameter)
-(keyword_parameter (identifier) @parameter)
+(method_parameters (identifier) @variable.parameter)
+(lambda_parameters (identifier) @variable.parameter)
+(block_parameters (identifier) @variable.parameter)
+(splat_parameter (identifier) @variable.parameter)
+(hash_splat_parameter (identifier) @variable.parameter)
+(optional_parameter (identifier) @variable.parameter)
+(destructured_parameter (identifier) @variable.parameter)
+(block_parameter (identifier) @variable.parameter)
+(keyword_parameter (identifier) @variable.parameter)
 
 ; TODO: Re-enable this once it is supported
 ; ((identifier) @function
@@ -159,13 +159,13 @@
  (simple_symbol)
  (delimited_symbol)
  (hash_key_symbol)
- ] @symbol
+ ] @string.special.symbol
 
 (pair key: (hash_key_symbol) ":" @constant)
-(regex) @string.regex
+(regex) @string.regexp
 (escape_sequence) @string.escape
 (integer) @number
-(float) @float
+(float) @number.float
 
 [
  (true)