feat(knurl): add Knurl cycle texture

Knurl follows the played note and treats every cycle of the wave on its
own: a repeating level pattern over 1-16 cycles makes subharmonics in tune
with every note, random level and timing per cycle add rattle, and a noise
burst per cycle, highpassed at a multiple of f0, adds grit. Amounts are
counted in cycles, so the texture is the same on F1 and on C2.

- Cycle clock from the shared note tracker, restarted at each note; the
  audio is delayed by the lookahead plus 4.2 ms of timing-jitter headroom.
- Per-cycle randomness from a hash of the cycle number: Same every note
  or Free.
- Patterns Off, Double, Triple, Fry (default), Gallop, Stutter or drawn;
  grit switchable per step. Pattern persisted as knurl-pattern.
- Editor: last eight cycles overlaid, pattern bars with the playing step.
- Tests match the prototype: Double gives f0/2 at -8.19 dB, Triple f0/3
  at -10.68 dB, equal on F1 and C2, no added clicks, bit-exact when off,
  no allocation on the audio thread.

plugins/catalog.json

@@ -114,5 +114,21 @@
       "weld-core",
       "weld-ui"
     ]
+  },
+  "knurl": {
+    "name": "Knurl",
+    "description": "Give every cycle of the note its own level, timing and grit",
+    "manifest": "plugins/knurl/plugin/Cargo.toml",
+    "library": "knurl",
+    "documentation": "docs/knurl",
+    "clap_id": "io.storyboard.cycle-texture",
+    "licenses": {
+      "plugins/common/ui/assets/OFL.txt": "licenses/Roboto-OFL.txt"
+    },
+    "packages": [
+      "common-ui",
+      "knurl-core",
+      "knurl-ui"
+    ]
   }
 }