[repo-assist] Fix front-matter parsing truncating values containing colons

RELEASE_NOTES.md

@@ -5,6 +5,9 @@
 ### Changed
 * Rewrote the Mermaid documentation recipe as `docs/mermaid.md` (moved from the oddly-named `docs/sidebyside/sidemermaid.md`) to follow the approach used by the fantomas docs: diagrams are written as plain ```mermaid fenced code blocks, which GitHub renders natively, and an `_body.html` script promotes those blocks into `<div class="mermaid">` elements on fsdocs pages. The FSharp.Formatting docs now ship that script (`docs/_body.html`), so the recipe page actually demonstrates working diagrams.
 
+### Fixed
+* Fix `FrontMatterFile.ParseFromLines` truncating front-matter values that contain a `:` character (e.g. `title: F#: An Introduction` was previously captured as just `F#`). Additional colons in a value are now preserved.
+
 ## [22.2.0] - 2026-08-31
 
 ### Changed

src/FSharp.Formatting.Common/Templating.fs

@@ -53,7 +53,7 @@ type FrontMatterFile =
                     let parts = line.Split(":") |> Array.toList
 
                     match parts with
-                    | first :: second :: _ -> Some(first.ToLowerInvariant(), second)
+                    | first :: rest when not rest.IsEmpty -> Some(first.ToLowerInvariant(), String.Join(":", rest))
                     | _ -> None
                 else
                     None)

tests/FSharp.Literate.Tests/DocContentTests.fs

@@ -745,3 +745,24 @@ let ``LlmsTxt collapses excessive blank lines in content`` () =
     llmsFullTxt.Contains("\n\n\n") |> shouldEqual false
     llmsFullTxt |> shouldContainText "First paragraph"
     llmsFullTxt |> shouldContainText "Second paragraph"
+
+// --------------------------------------------------------------------------------------
+// Tests for FrontMatterFile.ParseFromLines
+// --------------------------------------------------------------------------------------
+
+[<Test>]
+let ``ParseFromLines preserves colons in front-matter values`` () =
+    let lines = [ "---"; "title: F#: An Introduction"; "category: Guides"; "categoryindex: 2"; "index: 1"; "---" ]
+
+    match FrontMatterFile.ParseFromLines "test.md" lines with
+    | Some frontMatter ->
+        frontMatter.Category |> shouldEqual "Guides"
+        frontMatter.CategoryIndex |> shouldEqual 2
+        frontMatter.Index |> shouldEqual 1
+    | None -> failwith "Expected front matter to be parsed"
+
+[<Test>]
+let ``ParseFromLines returns None when required fields are missing`` () =
+    let lines = [ "---"; "title: No Category Here"; "---" ]
+
+    FrontMatterFile.ParseFromLines "test.md" lines |> shouldEqual None