refactor(comp): share C/JS show_chr and list/tuple brackets

[This-Is-NPC]

bend2/comp.ts only. Same language, same Base.

The C and JS showers repeated char-escape rules and list/tuple brackets.
One table now emits both.

• SHOW_ESC / SHOW_HEX emit show_chr. JS hex-escapes surrogates and
  code points past U+10FFFF the way C already did.
• SHOW_BR emits Con/Nil as [] and Tuple as ().

Net is about even (+39 / −37). The point is one readback policy, not fewer lines.

[zxv]

rescuing PR by commenting (github bug hid it temporarily)

[nicolas-abril]

While it is nice that we get the shared behaviour show_chr_src and show_br_c obscure the logic significantly and the code no longer follows the organization of the file, so I can't accept it as it is.

I think either hoisting only the part that is shared but keeping the C/JS skeletons there or applying just the C escape logic to JS would be good solutions