Extend glyph render constraints with cell-span sizing modes for height, width, contain, cover bounds, and stretch bounds. These preserve the existing face-targeted behavior for platform fonts, emoji, and Nerd Font rules while giving registered glyphs a target based on terminal cell spans. Map Glyph Protocol registration options to the new constraint modes so sizing follows the spec formulas based on authored advance width and line height. Baseline alignment now places design-space y=0 on the terminal text baseline instead of approximating it as start alignment. Document the placement formulas in the local protocol summary and add focused tests for constraint mapping, cell-span padding, line-height and advance scaling, contain versus cover behavior, stretch, and baseline placement.