perf: avoid ToCharArray allocations in TextConversions, HtmlParser, HtmlCssSelectors, HtmlOperations

- TextConversions.RemoveAdorners: replace ToCharArray()+Array.filter with a
  StringBuilder loop; avoids two intermediate char[] allocations (ToCharArray
  result + filtered result) on the hot path for every number/date parse attempt
- HtmlParser: replace ToCharArray()|>Array.rev string reversal with Array.init
  using direct index arithmetic; avoids ToCharArray allocation for malformed
  end-tag detection (e.g. <li></il>)
- HtmlCssSelectors.StartsWith: remove ToCharArray(); compare list against string
  directly via Seq.compareWith (string is IEnumerable<char>)
- HtmlCssSelectors.TokenStr: replace ToCharArray()|>Array.toList with List.ofSeq
- HtmlCssSelectors.Tokenize: replace ToCharArray()|>Array.toList with List.ofSeq
- HtmlOperations AttributeContainsPrefix: remove ToCharArray() before Seq.skipWhile
  since string is already IEnumerable<char>

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: github-actions[bot]

src/FSharp.Data.Html.Core/HtmlCssSelectors.fs

@@ -83,20 +83,18 @@ module internal HtmlCssSelectors =
             | c -> failwithf "Invalid css selector syntax at: %s" (new String(Array.ofList c))
 
         let (|StartsWith|_|) (s: string) (items: char list) =
-            let candidates = s.ToCharArray()
-
-            if items.Length < candidates.Length then
+            if items.Length < s.Length then
                 None
             else
-                let start = items |> Seq.take (candidates.Length) |> Seq.toList
+                let start = items |> Seq.take s.Length
 
-                if (Seq.compareWith (fun a b -> (int a) - (int b)) start candidates) = 0 then
+                if (Seq.compareWith (fun a b -> (int a) - (int b)) start s) = 0 then
                     Some(items |> Seq.skip s.Length |> Seq.toList)
                 else
                     None
 
         let (|TokenStr|_|) (s: string) x =
-            let chars = s.ToCharArray() |> Array.toList
+            let chars = List.ofSeq s
 
             let rec equal x s =
                 match x, s with
@@ -208,7 +206,7 @@ module internal HtmlCssSelectors =
 
         member public x.Tokenize(pCssSelector: string) =
             cssSelector <- pCssSelector
-            source <- cssSelector.ToCharArray() |> Array.toList
+            source <- List.ofSeq cssSelector
             charCount <- source.Length
             tokenize ()
 

src/FSharp.Data.Html.Core/HtmlOperations.fs

@@ -367,7 +367,7 @@ module HtmlNode =
                     let selectedNodes =
                         filterByAttr level acc name (fun v ->
                             let chars =
-                                v.ToCharArray()
+                                v
                                 |> Seq.skipWhile (fun c -> c = '\'')
                                 |> Seq.takeWhile Char.IsLetter
                                 |> Seq.toArray

src/FSharp.Data.Html.Core/HtmlParser.fs

@@ -1113,7 +1113,10 @@ module internal HtmlParser =
                 parse' docType elements expectedTagEnd parentTagName (TagEnd expectedTagEnd :: tokens)
             | TagEnd name :: rest when
                 name <> expectedTagEnd
-                && (name <> (new String(expectedTagEnd.ToCharArray() |> Array.rev)))
+                && (name
+                    <> (new String(
+                        Array.init expectedTagEnd.Length (fun i -> expectedTagEnd.[expectedTagEnd.Length - 1 - i])
+                    )))
                 ->
                 // ignore this token if not the expected end tag (or it's reverse, eg: <li></il>)
                 parse' docType elements expectedTagEnd parentTagName rest

src/FSharp.Data.Runtime.Utilities/TextConversions.fs

@@ -104,11 +104,14 @@ type TextConversions private () =
             // No adorners found, return original string to avoid allocation
             value
         else
-            // Adorners found, perform filtering
-            String(
-                value.ToCharArray()
-                |> Array.filter (not << TextConversions.DefaultRemovableAdornerCharacters.Contains)
-            )
+            // Adorners found, perform filtering via StringBuilder to avoid ToCharArray allocation
+            let sb = System.Text.StringBuilder(value.Length)
+
+            for c in value do
+                if not (TextConversions.DefaultRemovableAdornerCharacters.Contains(c)) then
+                    sb.Append(c) |> ignore
+
+            sb.ToString()
 
     /// Turns empty or null string value into None, otherwise returns Some
     static member AsString str =