feat(ballast): add Ballast switch-up leveller

Ballast gives every part of a bassline one gain that brings it to the target
loudness, with no compression inside a part. Parts start at note starts,
detected from the audio or taken from MIDI, or on the host's beat grid, so a
patch change on the same note counts too.

- Loudness is K-weighted over each part's first 100 ms, in 10 ms blocks with
  a relative gate, and every part is weighted from rest so the last part does
  not ring into it.
- The audio path is delayed by the tracker's lookahead, the window and a
  5 ms glide, so each gain is in place on its part's first sample.
- Learn takes the next part's loudness as the target. Amount, Range, Measure
  from (leave the sub out), Gate, Output, Bypass.
- Editor shows the last 32 parts in and out, the target, and the spread of
  the last 16 parts.
- Registered in the catalog, workflows, editor-check, README, chain and
  development docs, and the website copy.

plugins/catalog.json

@@ -182,5 +182,22 @@
       "quench-core",
       "quench-ui"
     ]
+  },
+  "ballast": {
+    "name": "Ballast",
+    "description": "Levels every note or switch-up to one loudness with a single gain each",
+    "manifest": "plugins/ballast/plugin/Cargo.toml",
+    "library": "ballast",
+    "documentation": "docs/ballast",
+    "clap_id": "io.narl.bass-foundry.ballast",
+    "licenses": {
+      "plugins/common/ui/assets/OFL.txt": "licenses/Roboto-OFL.txt"
+    },
+    "packages": [
+      "common-ui",
+      "common-dsp",
+      "ballast-core",
+      "ballast-ui"
+    ]
   }
 }