The LED work had a hole in the middle of it. `lcxl-leds.py --watch` was
written, wired into the boot sequence and into gig-up.sh, and validated only
against a FAKE aseqdump stream — nobody, human or machine, had ever seen it
light a single LED. PLN kept reporting "still seeing static colors" and I had
no way to check my own work, because I cannot look at the device.

mock-lcxl decodes the same SysEx the real surface receives and renders it in
the terminal, so the convention can be designed, reviewed and regression-tested
without hardware. The only thing still needing PLN's eyes is whether the
physical LEDs match the picture.

It answered the "static yellow" complaint on its first run. Painting
claude.tidal lights knobC 1-3 BRIGHT AMBER (63) — which is exactly
filter_colour(64), the DJ filters resting at centre. Our code is working as
designed; the design is the problem. Bright amber at rest is visually
indistinguishable from the factory yellow PLN is trying to get away from, so
"correct" and "looks broken" are the same picture. Second finding, same run:
control_colour returns hue["full"] for every value from 8 to 119, so a touched
knob is one flat bright colour across its whole travel. Touch changes it once
and then it never moves again — which is precisely what he has been describing.

So value_ramp() implements his spec verbatim — "from dim red nothing through
bright red dim orange bright orange dim green bright green at max". That is
six steps, and six is not a coincidence: the LCXL is bicolor (2 bits red x 2
bits green = 16 states) and only about six read reliably on a dim stage. The
ramp uses the entire usable budget and spends nothing on shades nobody can
tell apart. `mock-lcxl.py --palette` shows the whole budget; --ramp shows the
convention resolving across 0..127.

The DJ filters deliberately keep filter_colour and do NOT get the ramp: they
are bipolar, centre 64 is bypass, and a monotonic red->green ramp would paint
bypass as mid-orange and the two opposite musical extremes as the same colour.

8 regression tests covering the ramp order, monotonicity, "a mapped control at
zero is dim, never off" (a control you cannot see is one you forget exists),
"a filter is never dark", and a SysEx round-trip through the mock surface.