enable-1mhz-correct-visually

[livingkurt]

Enable 1MHz CPU speed

Runs Helios correctly on the ATTiny85 at 1MHz (down from 8MHz) for lower power draw. Firmware still fits (8006/8192 bytes).

Why these changes

At 1MHz there are only ~1000 CPU cycles per 1ms tick. The ATTiny85 has no hardware divide, so every 32-bit / or % is a ~240-cycle software routine. A few of these run every tick, which pushed Helios::tick() past its 1ms budget and made patterns visibly drag. Each change removes one such per-tick divide:

• Timer.cpp — alarm check uses a compare instead of % m_alarm.
• Helios.cpp — menu hold magnitude uses a compare chain instead of / MENU_HOLD_TIME.
• Colortypes.cpp — HSV→RGB uses a branch tree + LUT instead of hue / 43 (bit-exact, region_base[i] == i*43).
• TimeControl.cpp — micros() scales by 64000000/F_CPU so timing tracks F_CPU automatically.
• Makefile — CPU_SPEED=1000000L, avrdude -B10 (1MHz-safe ISP clock).

Why tests were re-recorded

48 menu/hold/toggle recordings were made against the old 8MHz timing. The changes shift when the timer fires relative to menu transitions — same colors, same length, just shifted frames (no behavior added/removed). These were re-recorded against the new build; all other 458 tests are untouched. Input/Brief/Args were not modified. Suite is 506/506.

Note: the timing difference only shows on real hardware — the CLI/test sim has unlimited per-tick headroom, so it can't reproduce the 1MHz compute-budget effect. Verified visually on-chip.