starkernel: item 4.4f -- fix vertically-flipped glyph rendering on the framebuffer

font_8x16_data stores each glyph's 16 scanline bytes bottom-to-top, not
top-to-bottom -- confirmed by hand-decoding 'A' (0x41) and 'T' (0x54): both
only produce their correct letterform when the row order is reversed.
fb_draw_glyph() mapped glyph row 0 to the cell's top pixel row, which was
wrong for this table. Flip the row-to-pixel mapping instead of touching the
4096-byte font data; every glyph now renders right-side up.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/starkernel/hal/framebuffer.c

@@ -189,7 +189,10 @@ void fb_draw_glyph(uint32_t px, uint32_t py, uint8_t ch,
             uint32_t on     = (bits >> (7u - col)) & 1u;
             uint32_t packed = on ? pfg : pbg;
             uint32_t base_x = px + col  * g_fb.scale;
-            uint32_t base_y = py + row  * g_fb.scale;
+            /* font_8x16_data stores each glyph's scanlines bottom-to-top
+             * (FABRIC.md item 4.4f) -- row 0 is the glyph's bottom row, so
+             * it maps to the cell's last pixel row, not its first. */
+            uint32_t base_y = py + (15u - row) * g_fb.scale;
 
             /* pixel block for scale > 1 */
             for (sr = 0; sr < g_fb.scale; sr++) {