P10.9: use real Match FX cues for the cascade combos

Replace the pitch-laddered single-pop combo ladder with FIVE distinct REAL
Match FX cues from the user's Triple Treat SFX pack (Match SFX/), ordered to
convey cascade escalation by spectral brightness / high-frequency energy
(combo1 dullest -> combo5 sparkliest):

  combo1 <- Match SFX/Match FX 2-RCM.wav  (dark/full,   centroid ~1.7 kHz)
  combo2 <- Match SFX/Match FX 4-RCM.wav  (warm mid,    centroid ~2.1 kHz)
  combo3 <- Match SFX/Match FX 6-RCM.wav  (bright mid,  centroid ~3.2 kHz)
  combo4 <- Match SFX/Match FX 7-RCM.wav  (rich+bright, centroid ~4.7 kHz)
  combo5 <- Match SFX/Match FX 3-RCM.wav  (sparkly,     centroid ~6.8 kHz)

The Match FX set does not cleanly pitch-ascend, so brightness is the ordering
signal; spectral centroid ascends monotonically 1.68 < 2.09 < 3.18 < 4.70 <
6.77 kHz. Each down-mixed to mono, trimmed to a 0.50 s onset window, eased in
(~6 ms) and rounded out with a 150 ms cosine fade-out, peak-normalized -15 dBFS.

Pure drop-in: audio.sx and all wiring are untouched; swap/match/win/lose are
byte-identical to P10.8. The depth->cue-index mapping (cascade_cue, fx_combo)
locks the integer mapping, not the audio content, so both tests stay valid.
LICENSE.txt combo provenance updated to the real Match FX sources.

assets/audio/LICENSE.txt

@@ -36,16 +36,22 @@ match.wav   — bright, juicy candy POP (the satisfying first-clear reward).
               Source: Pop:Bubble SFX/Pop FX 5-RCM.wav
               Trimmed to the single pop (~0.44 s), faded, peak-normalized -15 dBFS.
 
-combo1..5.wav — the candy-cascade ladder: ONE clean pop pitch-laddered up a
-              major-pentatonic run (+0/+2/+4/+7/+9 semitones) so deeper cascades
-              pop higher. The pack's Match FX set does NOT ascend monotonically,
-              so a single good pop was real-resample pitch-shifted instead.
-              Source: Pop:Bubble SFX/Pop FX 3-RCM.wav
-              Real DSP (linear-interpolation resample) per step; trimmed
-              (~0.36 s down to ~0.21 s as pitch rises), faded, peak-normalized
-              -15 dBFS. Measured fundamentals (tools/measure_pitch.py), strictly
-              ascending:
-                combo1 687 Hz < combo2 771 < combo3 865 < combo4 1029 < combo5 1155
+combo1..5.wav — the candy-cascade ladder: FIVE distinct REAL Match FX cues from
+              the pack, ORDERED to convey cascade escalation. The Match FX set
+              does not cleanly pitch-ascend, so the cues are ordered by spectral
+              brightness / high-frequency energy instead — combo1 the dullest /
+              most subdued, combo5 the brightest / sparkliest, so deeper cascades
+              read as more exciting.
+                combo1 — Match SFX/Match FX 2-RCM.wav  (dark/full,   centroid ~1.7 kHz)
+                combo2 — Match SFX/Match FX 4-RCM.wav  (warm mid,    centroid ~2.1 kHz)
+                combo3 — Match SFX/Match FX 6-RCM.wav  (bright mid,  centroid ~3.2 kHz)
+                combo4 — Match SFX/Match FX 7-RCM.wav  (rich+bright, centroid ~4.7 kHz)
+                combo5 — Match SFX/Match FX 3-RCM.wav  (sparkly,     centroid ~6.8 kHz)
+              Each down-mixed to mono, trimmed to a 0.50 s onset window, eased in
+              (~6 ms) and rounded out with a 150 ms cosine fade-out, peak-
+              normalized -15 dBFS. Brightness (spectral centroid) ascends
+              monotonically, conveying escalation:
+                combo1 1.68 < combo2 2.09 < combo3 3.18 < combo4 4.70 < combo5 6.77 kHz.
 
 win.wav     — short, triumphant POWER-UP cue (level won).
               Source: Success:Power-Up SFX/Power Up FX 1-RCM.wav