SB-002-TERMINAL_CORE.md (P0, 297 lines)

• Core terminal emulation with VT100/ANSI compatibility
• Data structures: d3tui_term_config_t (width, height, scrollback, colors, cursor blink), d3tui_cell_t (codepoint, fg/bg color, attributes), d3tui_terminal_t (opaque)
• Public API: create/destroy, input (putc/puts), state queries (get_cell, get_cursor), buffer ops (clear, scroll), scrollback navigation, configuration
• Default 16-color VGA palette defined as D3TUI_DEFAULT_PALETTE[16]
• Supported escape sequences: cursor home/movement, erase, attributes (bold/underline/reverse), colors (16 foreground + 16 background), scroll regions, save/restore cursor
• Performance targets: buffer updates < 1ms for 80x25, scrollback < 10ms for 1000 lines
• Memory budget: ~38.4KB for 80x60 + scrollback mitigation via 256-line limit