[Repo Assist] fix: use ctx.Newline in ToMd table rows and ToFsx output comments

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Summary

Two targeted bug fixes for hardcoded "\n" newline usage in the Markdown serialisers.

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1. Markdown.ToMd — TableBlock rows used hardcoded "\n" (Task 3 — bug fix)

Root cause

formatParagraph for TableBlock collected all data rows into a single string with String.concat "\n", then yielded that one big string. The trailing blank-line was emitted as yield "\n" (a literal newline character string) rather than the standard yield "" (empty-line sentinel) used by all other paragraph types.

Effect

On Windows (ctx.Newline = "\r\n"), Markdown.ToMd produced mixed line endings in the output: headers and alignments used \r\n (from the outer String.concat newline), while data rows used \n (from the hardcoded String.concat "\n" inside). The trailing blank was also a bare \n.

Fix (src/FSharp.Formatting.Markdown/MarkdownUtils.fs)

• Replaced the single-yield [for r in rows ...] |> String.concat "\n" with a for r in rows do yield ... loop, so each data row is emitted as a separate string item.
• Changed yield "\n" → yield "", consistent with all other paragraph types.

The outer String.concat newline in formatAsMarkdown now correctly joins data rows with the configured newline.

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2. Markdown.ToFsx — output-comment used hardcoded "\n" (Task 5 — coding improvement)

Root cause

FsxFormatting.fs opened the (* output: ...*) comment with a literal "\n":

| _out -> "(* output: \n" + output + "*)")

The output string was already built with ctx.Newline, but the opening comment-marker used a Unix newline regardless.

Fix (src/FSharp.Formatting.Markdown/FsxFormatting.fs)

• Changed "(* output: \n" → "(* output: " + ctx.Newline so the entire comment uses consistent line endings.

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Tests added (tests/FSharp.Markdown.Tests/Markdown.fs)

• ToMd table rows each appear on their own line — parses a two-row table, serialises with newline = "\n", and asserts the non-blank lines equal exactly 4 (header + separator + 2 data rows).
• ToMd table row count is correct when Windows newline is used — regression test: serialises with newline = "\r\n" and asserts there are no stray \n embedded in the output (no \r\n\n or \n\r\n sequences).

Test Status

• ✅ dotnet build FSharp.Formatting.sln --configuration Release — succeeded (0 warnings, 0 errors)
• ✅ dotnet test tests/FSharp.Markdown.Tests — 348/348 passed (includes 2 new tests)
• ✅ dotnet fantomas ... --check — formatting verified (no changes needed)
• ✅ dotnet test FSharp.Formatting.sln --configuration Release --no-build — full suite passes (Literate: 143, ApiDocs: 88+4 skipped, CodeFormat: 30, fsdocs-tool: 12, Markdown: 348)

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