PHLEGM v6 Machine CLEAR command

- Adds CLEAR as a console/GUI machine command.
- GUI order: On, Off, Reset, Eject, Clear, Fry, Hex Editor.
- Embedded instruction-definition version is bumped so existing installs regenerate PHLEGM.gui.phlegm and gain the new/ordered entries.
- Eject and Fry stay visible whenever a machine is selected; unsupported machines report the normal command-level applicability message.
- CLEAR preserves the selected machine, loaded firmware, and inserted media identity.
- Clears writable VM memory/register state, support-chip runtime state, cartridge PRG RAM / CHR RAM, DMA/interrupt/timing state, display latches/history, and presentation readiness.
- Rebuilds the active 64K bus lookup after remapping firmware/cartridge.
- If powered ON, restarts from the machine reset vector. If powered OFF, remains OFF.
