Add UG #8 / #9 sweep presets, remove Elite: dying and Thrust: explosion

Two BBC User Guide-style examples added that exercise the chip's pitch
register wrap and large multi-section pitch envelopes:

- UG #8 sweep: -26/-36/-45 PI deltas over 255 steps each, held loud,
  with the 8-bit pitch register wrapping continuously.
- UG #9 ramp: +2/-4/+4 PI over 50 steps each, net upward drift over
  a long held tone.

Removed Elite: dying and Thrust: explosion since they did not
audition cleanly under the new envelope timing model.

Author: kieranhj

src/presets.ts

@@ -149,13 +149,6 @@ export const PRESETS: Preset[] = [
            aa: 6, ad: 1, as: 0, ar: -2, ala: 120, ald: 126 },
     sound: { channel: 2, amplitude: 2, pitch: 44, duration: 8 },
   },
-  {
-    name: "Elite: dying",
-    description: "Elite — first part of the death sound; also used for hits/kills (envelope 3)",
-    env: { n: 3, t: 1, pi1: 1, pi2: -1, pi3: -3, pn1: 17, pn2: 32, pn3: 128,
-           aa: 1, ad: 0, as: 0, ar: -1, ala: 1, ald: 1 },
-    sound: { channel: 1, amplitude: 3, pitch: 240, duration: 24 },
-  },
   {
     name: "Elite: ECM",
     description: "Elite — E.C.M. (Electronic Counter Measures) firing; envelope 4 with sweeping pitch over a long duration",
@@ -177,13 +170,6 @@ export const PRESETS: Preset[] = [
            aa: 126, ad: -7, as: -7, ar: -12, ala: 126, ald: 0 },
     sound: { channel: 2, amplitude: 1, pitch: 80, duration: 2 },
   },
-  {
-    name: "Thrust: explosion",
-    description: "Thrust — explosion tone component on channel 1 (envelope 2; the original game pairs this with a parallel noise burst)",
-    env: { n: 2, t: 2, pi1: -1, pi2: 0, pi3: 1, pn1: 9, pn2: 9, pn3: 9,
-           aa: 0, ad: 0, as: 0, ar: 1, ala: 1, ald: 1 },
-    sound: { channel: 1, amplitude: 2, pitch: 150, duration: 40 },
-  },
   {
     name: "Thrust: hostile",
     description: "Thrust — hostile gun firing (envelope 4)",
@@ -248,4 +234,18 @@ export const PRESETS: Preset[] = [
            aa: 121, ad: -10, as: -5, ar: -2, ala: 120, ald: 1 },
     sound: { channel: 1, amplitude: 1, pitch: 100, duration: 40 },
   },
+  {
+    name: "UG #8 sweep",
+    description: "BBC User Guide example — large negative pitch deltas wrap the chip's 8-bit pitch register, producing a rapidly cycling sweep. Held loud (AA=127, AR=0) over a short SOUND duration so the wrapping pitch is the dominant feature.",
+    env: { n: 1, t: 1, pi1: -26, pi2: -36, pi3: -45, pn1: 255, pn2: 255, pn3: 255,
+           aa: 127, ad: 0, as: 0, ar: 0, ala: 126, ald: 0 },
+    sound: { channel: 1, amplitude: 1, pitch: 1, duration: 1 },
+  },
+  {
+    name: "UG #9 ramp",
+    description: "BBC User Guide example — three-section pitch envelope with large excursions (rise +100, drop -200, rise +200 per loop). Net +100 per loop produces an upward-drifting sweep over a long held-loud tone.",
+    env: { n: 2, t: 3, pi1: 2, pi2: -4, pi3: 4, pn1: 50, pn2: 50, pn3: 50,
+           aa: 127, ad: 0, as: 0, ar: 0, ala: 126, ald: 0 },
+    sound: { channel: 1, amplitude: 2, pitch: 1, duration: 10 },
+  },
 ];