Always use aixterm bright color codes for bright colors

[sdairs]

Bright foreground colors (GRAY through WHITE, codes 8-15) were emitted as aixterm bright color codes (90-97) only when TERM contained the substring "256", falling back to bold + dark color (e.g. \e[0;1;30m for GRAY) otherwise.

The check is misguided: codes 90-97 belong to the basic 16-color set and are unrelated to 256-color support. Meanwhile the fallback breaks on terminals with TERM values like xterm-ghostty, xterm-kitty, alacritty or foot, because modern terminals do not render bold as bright by default: GRAY (bold black) degrades to plain black. In ClickHouse this makes the as-you-type autocompletion hints, which default to GRAY, unreadable on dark backgrounds in Ghostty (while the same build looks fine under TERM=xterm-256color).

This change emits the bright color codes unconditionally.

Verified by linking ansi_color into a small harness with TERM=xterm-ghostty:

Color	Before	After
GRAY	\e[0;1;30m (bold black)	\e[0;90m (bright black)
BRIGHTRED	\e[0;1;31m	\e[0;91m
WHITE	\e[0;1;37m	\e[0;97m
RED	\e[0;22;31m	\e[0;22;31m (unchanged)
DEFAULT	\e[0m	\e[0m (unchanged)

🤖 Generated with Claude Code

Backward compatibility

• No change for TERM values containing "256" (e.g. xterm-256color, the default on desktop Linux terminals since ~2010) — they already received codes 90-97.
• Codes 90-97 are the aixterm extension of the basic 16-color set, supported for decades by xterm (since the late 1990s), PuTTY, rxvt, GNU screen, tmux, Konsole and all VTE-based terminals.
• Terminals that do not implement 90-97 (e.g. the physical Linux console on kernels before ~4.17, monochrome hardware terminals) ignore the unrecognized SGR parameter per ECMA-48; the leading 0 in \e[0;9Xm still resets attributes, so text renders in the default foreground — readable, merely uncolored. The failure mode of the old code was worse: bold black rendered as invisible text on dark backgrounds.
• Only interactive TTY rendering is affected: replxx checks is_a_tty before emitting attributes, so piped output never contains these sequences.
• replxx does not consult terminfo; all of its escape sequences (dark colors, cursor movement, \e[J) are hardcoded ANSI, so this change stays within the library's existing ECMA-48 assumption.