feat(tools): set-coherence — 108 controls sit idle under his hand, and three of them are systematic (#113)

PLN, 2026-07-31, having walked the OPAL set by eye:

  "when i went across set i saw some unmapped effects/button, a 'set coherence
   mapping review' and quick wins suggestions (bass octersub, lead slice, etc etc)
   could be good ways for you to fill-in suggest"

He was right, and the number is larger than "some": **108 idle slots across 117
declared orbits in the 13 setlist tracks.**

## Why this needed a tool rather than a read-through

Absence has no line number. The surface is a fixed grid — each orbit owns a known set
of cells (effect knob, maybe a second, gate button, maybe a second) — so a track that
declares d5 and never references ^33 leaves d5's knob inert for that track's whole
duration. You cannot grep for a control that isn't there; you can only compute it, by
subtracting what the track USES from what the orbit OWNS.

The tool reports both directions of the same coherence question, deliberately:
  IDLE     orbit owns a slot the track never uses   -> unused affordance (new)
  STARVED  track drives more controls than it owns  -> already covered by PV008
                                                       and the FIXME(#54)/(#94) markers
Fixing one can create the other, which is why they belong in one report.

## Three systematic findings, not a flat list

1. **The drums' own effect knobs are the deadest controls on the board.**
   d2.fx (B2 ^30) idle in 12/13 tracks, d1.fx (B1 ^29) 9/13, d3.fx (B3 ^31) 8/13.
   d1-d3 own exactly ONE per-orbit knob each — their row-C cells are the family
   filters — so this is not a spare slot going unused, it is their only knob. The
   KICK has no per-orbit effect knob bound anywhere in the entire set.

2. **Row A (d9-d12 effects, A5-A8) is ~90% idle.** d11 6/6, d12 5/5, d10 6/7, d9 5/8.
   That is #98's proposal (pool A5-A8 in order of appearance) with its supporting
   numbers: four knobs almost never used, on exactly the orbits that overflow.

3. **d6 has gates but NO knobs, 5 of 5 tracks.** Fallout from the d7->d6
   consolidation: ^58/^90 came along, ^34/^54 did not. And vague_de_crime's d6
   references nothing at all — no knob, no gate.

## Suggestions are grounded, not invented

Measured what PLN actually binds to a per-orbit effect knob across the set — perc
legato(4); bass lpf(3), gain(1), bandf(1); lead width(2), modIndex, filterRange,
cutoff, resonance; kick nothing — and the suggestion table echoes that idiom before
extending it (memory feedback_self_reference_rhythm_study: extract the grammar from
his own tracks rather than importing generic Tidal advice).

Worth recording because it inverts the ask: his two named wants sit OUTSIDE his
measured idiom. He binds lpf to bass knobs and never octersub; slice lives on his
buttons, not his knobs. So "bass octersub, lead slice" are additions he is reaching
for, not corrections of drift — and saying so is more useful than pretending the
corpus already implied them.

## Deliberately not applied
Every suggestion changes how a track sounds and he is rehearsing on these files this
weekend. Output is docs/2026-07-31-set-coherence.md to skim and cherry-pick. The tool
also never suggests binding CC 77-84 / 13-16 (Ardour track gains), 93 (gPanic), or the
family cells 49/50/51 + 73/74/75.

Also confirms the #94 remap held: "borrowed" CCs — ones an orbit drives without owning
— are 0 or 1 across every track in the set.