Put a sound in a room, a hall or a cave with a Reverb node (#328)

A sound FX had no space around it. The Reverb node folds the sound
with an impulse response: one it makes itself, or a sound asset as the
answer of a real space. It works on a voice and on a bus.

- Type: Room, Hall, Cave and Plate have fixed numbers. Custom shows
  Decay (up to 10 s), Damping and Pre-delay. Sound shows the pick of a
  sound asset and Pre-delay. The rows are derived ports, the sound pick
  an idle param, so they only appear for their type.
- The made impulse response is seeded noise per side, 60 dB down at
  Decay, through a low-pass closing from 20 kHz toward 500 Hz as far
  as Damping says. It is made once per rate, decay and damping, the
  last 16 are kept.
- A sound as impulse response: the sound FX compilers now get the
  project, so a node can turn a sound asset into its file. The build
  key holds that file, so a cut or swapped sound builds again. The
  instrument compiler does the same for a Reverb inside an instrument.
- The library loads that file with the voice, a sequence or before a
  bus builds its chain. A missing file leaves the reverb silent.
- Mix blends dry and reverb and is the only number that moves while
  the sound plays, as the issue said. The voice rings for pre-delay
  plus decay, or as long as its sound.
- The open point from #325 about sends on project buses is #351, not
  part of this.

Tests:
- Unit reverb (new) 4, soundfx 57 (4 new), sound-library 104 (2 new),
  green.
- Counter-checks, each turns one test red: the impulse file not loaded
  with the voice, the tail without the length of the sound.
- e2e 34 (melektaus-atx): ALL PASSED, 81 checks (1 new). Chrome
  offline: silent during the pre-delay, 35.9 dB fall over 0.6 s of a
  1 s decay (36 expected), the dry half at 0.25 for mix 0.5. A sound
  with one sample at 0.2 s gives the impulse back 0.25 s later and
  nowhere else.
- Gate (melektaus-atx) over the end of this series #318 to #328:
  CHECK EXIT 0, 267 files, 4134 tests.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/core/instrument/compile.ts

@@ -18,7 +18,7 @@ import { findAssetOf, type Project } from '../model/Project';
 import { playedSoundOf } from '../properties/playedSound';
 import { resolveAssetProps } from '../properties/resolve';
 import { volumeOf } from '../properties/sounds';
-import { soundFxBuildFor } from '../soundfx/compile';
+import { soundFxBuildFor, soundFxKey } from '../soundfx/compile';
 import {
   type FxAmount,
   type FxChipPlan,
@@ -32,6 +32,8 @@ import {
   SOUND_FX_OUTPUT,
   SoundFxMix,
   type SoundFxNodeDef,
+  type SoundFxProject,
+  SoundFxReverb,
   withPitch,
   withStages,
 } from '../soundfx/nodes';
@@ -83,13 +85,13 @@ export function instrumentSourcesOf(project: Project): InstrumentSources {
     },
     soundFx: (assetId) => {
       const asset = findAssetOf(project, assetId, 'soundfx');
-      return asset ? soundFxBuildFor(asset).compiled : null;
+      return asset ? soundFxBuildFor(asset, project).compiled : null;
     },
     key: (assetId) => {
       const sound = findAssetOf(project, assetId, 'sound');
       if (sound) return `${playedSoundOf(project, sound)}@${volumeOf(resolveAssetProps(project, sound))}`;
       const fx = findAssetOf(project, assetId, 'soundfx');
-      return fx ? graphFingerprint(fx.graph) : '';
+      return fx ? soundFxKey(fx, project) : '';
     },
   };
 }
@@ -130,6 +132,7 @@ export function instrumentParams(graph: Graph): readonly DeclaredPort[] {
  * are numbers here, `velocity` and the parameters stay open for every voice to fill in.
  */
 export function compileInstrument(graph: Graph, note: number, sources: InstrumentSources): InstrumentBuild {
+  const project: SoundFxProject = { soundFile: (assetId) => sources.sound(assetId)?.file ?? '' };
   const walk = graphEmitter<Def, Value>(graph, {
     isDef: isInstrumentDef,
     noun: 'instrument',
@@ -224,10 +227,12 @@ export function compileInstrument(graph: Graph, note: number, sources: Instrumen
       const [a] = plansAt('a');
       const [b] = plansAt('b');
       if (!a || !b) return { out: { plans: a ? [a] : b ? [b] : [] } };
-      return { out: { plans: [def.emit({ a, b }, amounts, node.params)] } };
+      return { out: { plans: [def.emit({ a, b }, amounts, node.params, project)] } };
     }
     const [arriving] = plansAt('in');
-    return { out: arriving ? { plans: [def.emit({ in: arriving }, amounts, node.params)] } : SILENT };
+    return {
+      out: arriving ? { plans: [def.emit({ in: arriving }, amounts, node.params, project)] } : SILENT,
+    };
   }
 
   /** A Sample's sound, or null after saying why it has none – also where its trigger is off. */
@@ -383,7 +388,12 @@ export function instrumentBuildFor(
   sources: InstrumentSources,
 ): InstrumentBuild {
   const named = asset.graph.nodes
-    .map((node) => textOf(node.params[node.type === INSTRUMENT_SOUND_FX ? 'fx' : 'sound'] ?? ''))
+    .flatMap((node) =>
+      node.type === INSTRUMENT_SOUND_FX
+        ? [node.params.fx]
+        : [node.params.sound, ...(node.type === SoundFxReverb.type ? [node.params.impulse] : [])],
+    )
+    .map((id) => textOf(id ?? ''))
     .filter((id) => id !== '');
   const fingerprint = `${graphFingerprint(asset.graph)}|${named.map((id) => sources.key(id)).join('|')}`;
   let cached = builds.get(asset.id);