[Feature] Add extended color support (True Color & 256‑color) with rgb / hex / color256

[razbuild]

Feature request

Currently RazTint only supports the 16 standard ANSI colors. Add optional, zero‑dependency support for extended colors: 24‑bit True Color and 256‑color mode via raw ANSI escape sequences.

Proposed API

from raztint import rgb, hex_color, color256
from raztint import bg_rgb, bg_hex_color, bg_color256

# True Color foreground
print(rgb("This is orange text", 255, 100, 50))
print(hex_color("Same orange via hex", "#FF6432"))

# True Color background
print(bg_rgb("Orange background", 255, 100, 50))

# 256-color
print(color256("Orange via 256 palette", 208))
print(bg_color256("Background 256", 208))

# Seamless composition with existing styles
print(bold(rgb("Bold green text", 0, 200, 0)))
print(rgb(bg_color256("White text on orange bg", 208), 255, 255, 255))

Acceptance criteria

• Zero dependencies – only stdlib escape codes

• All new functions follow the pattern func(text, *color_params) → str

• ANSI sequences: \033[38;2;R;G;Bm (foreground), \033[48;2;R;G;Bm (background)

• 256‑color: \033[38;5;INDEXm / \033[48;5;INDEXm

• Respect NO_COLOR, RAZTINT_FORCE_COLOR, and terminal detection

• Works with existing styling functions (bold, underline, etc.)

• Backward compatible – doesn’t break red(), bg_blue(), etc.

• Background color resets use \033[49m to preserve foreground styles

• Unit tests for each new function

• README updated with an “Extended Colors” section

• New code passes project tooling: black src tests, ruff check src tests, and ty check src