Graphics Refactor 2026-05

[WillGreen]

Many small fixes and improvements from recent work on future Isle graphics and device designs.

• display_timings.v and display_modes.vh replace display.v
  • replace hres/vres signals with params
  • add params for bitmaps
• reduce textmode latency in font_glyph so tram can have output reg
• improve latency param calculations
• handle clut/background colour latency properly
• add 1920x1080p support on XC7 boards
• move chapter 6 device modules under hardware/book/ch06
• add report_timing_summary to Vivado builds
• parameterise ch01 to work with any display mode
• use 672x384 display mode for Verilator ch01 design
• rename signals for clarity
• reorder lines to ensure signals/params aren't used before definition