💡 Border style variety (named styles + custom charset)

[natemoo-re]

Is your feature request related to a problem?

We can only draw one style of border. The renderer hardcodes every glyph—corners ┌┐└┘, horizontals ─, verticals │. When cornerRadius > 0, the corners are swapped for ╭╮╰╯ .

Describe the solution you'd like

Callers should be able to pick from CSS border-style (to the extent possible), and potentially custom glyphs.

"double" would select ╔╗╚╝ / ═ / ║; a custom object maps each position (topLeft, top, topRight, right, bottomRight, bottom, bottomLeft, left) to a string drawn verbatim:

const border = {
  color: rgba(255, 255, 255),
  left: 1,
  right: 1,
  top: 1,
  bottom: 1,
  charset: "double", // or others
};

Describe alternatives you've considered

Drop our border and paint the box as raw text cells, which loses the layout engine's border reservation, junction handling, and per-side widths—reimplementing the border renderer in user space.

Additional context

Failing test case on nm/repro/border-styles (test · diff); charset is dropped today, so single-line glyphs render regardless. The change likely lives in render_border at src/clayterm.c:300 and the cornerRadius-keyed ternaries at src/clayterm.c:310-313, with the wire format threading a style/glyph field through ops.ts:256, ops.ts:138-149, and the PROP_BORDER decode at src/clayterm.c:530-537.

Implementation is in progress on feat/border-style and may be closed by its PR.