Tables rendered through `<Md>` had no separator and no header weight,
so they read as a paragraph with extra whitespace. This adds two tiny,
border-free changes that survive Ink's grapheme-approximate column
widths better than a full outline:
* Bold the header row, keeping the existing amber colour.
* Insert a dim `─`-dashed rule between the header and body rows.
We deliberately stay away from a full outline — column widths are
measured via `stripInlineMarkup(...).length`, which is grapheme-aware
but still off by a cell on East Asian wide characters and emoji-mid-
cell strings. A header rule plus the existing 2-space column gap
gives the visual hierarchy the issue asks for without amplifying that
inaccuracy into a misaligned border.
Validation: `npm run type-check` clean, `npm test --run` 389/389.
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