PHLEGM v4 - top-level CHR GUI drop-down

The graphical command tree now exposes CHR as its own top-level drop-down.

CHR
  Status
  LOAD - /data/chr/ .BIN + recursive ZIPs
  PREVIEW - effective active CHR
  SAVE <file.bin> - export effective CHR
  UNLOAD - restore original CHR
  Firmware write state [Commodore character-ROM machines only]
    Toggle
    Writable
    Read-only

LOAD remains lazy and recursive. Expanding it scans data/chr/ for loose .BIN files, subdirectories, ZIP files, and nested ZIP containers. Single-clicking a BIN leaf previews it without loading; double-click loads it.

The former duplicate CHR branches under Memory / Program and Configuration / Machine I/O were removed so the top-level CHR branch is the canonical GUI location. Console commands remain unchanged.

Embedded instruction-definition version: 17.
