GLIDE v3.0 — custom themes, wah, gate

Three additions and one correction. No new gestures, no new settings rows —
everything below rides controls that already existed.

Custom themes

The Theme setting gains an eleventh entry, custom, after the ten built-in
palettes. Selecting it reveals five dials directly beneath it:

• Hue — the instrument's colour. Everything else is defined relative to it,
  so turning this one dial rotates the whole palette.
• Accent — the angle from that hue to the annunciator colour. Shown as a
  relationship (same / near / wide / triad / split / opposite).
• Vividness — saturation.
• Ground — the background, from black through dusk and ash up to
  paper and bright. Crossing into the light half switches the instrument to
  its light-background colour model.
• Contrast — how far the text and trace sit from the background.

A sixth row, Roll look, generates a complete palette at once.

Cycling onto custom from a palette you were already using starts you with a
copy of that palette rather than a default. Every combination is held to a
minimum contrast against the background, so no dial position can make the
screen unreadable.

The dials are hidden unless Theme is set to custom, so nothing changes for
anyone who doesn't use it. Your palette is stored on the device, not in the
firmware, so it survives future updates.

Two new G0 trigger actions

Settings → TRIGGER → Trigger action:

• wah (sweeps) — a resonant filter peak sweeps 350 Hz to 2.4 kHz, one sweep
  every two beats. At full depth the sweep replaces the patch's own cutoff, and
  resonance goes to maximum. Both the solo and the backing layer sweep.
• gate (16ths) — the output is chopped on sixteenth notes, including the
  reverb tail. The metronome is not gated.

Both lock to the instrument's tempo, so tap tempo (\) and the BPM setting move
them. Both restart their cycle each time you press G0. Trigger depth scales
them from subtle to extreme, and both do nothing at 0%. Latch mode works as it
does for the existing actions — tap G0 once and the effect keeps running.

The ` key now says "restart"

Holding ` saves your work and reboots, and the Cardputer boots straight
back into GLIDE — the Launcher does not appear. The labels said "exit", which
was wrong. They now say "restart".

To reach Launcher, press BTN RST (the left trigger on the top edge) and tap
any key as the device comes up.

Documentation

docs/manual.md now documents the Theme setting and the custom palette dials,
which it had never covered, and its trigger-action list now includes synth morph, which was missing.

Install

Copy GLIDE.bin to /apps on your SD card, or update through M5Launcher.
NOTICES.txt is the third-party licence attribution and should ship with any
copy of the binary.