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.

docs/development.md

@@ -25,7 +25,8 @@ Patina has `render` for offline WAV evaluation. The shared crates are:
 
 - `common-ui`: palette, embedded fonts, header, panels, knobs, meters.
 - `common-dsp`: filters, YIN pitch tracking, the note tracker used by Anvil,
-  Lathe, Temper, Knurl, Planish and Braze, 4× oversampling (also Quench's), meters and WAV files.
+  Lathe, Temper, Knurl, Planish, Braze and Ballast, 4× oversampling (also Quench's),
+  BS.1770 K-weighting (Ballast), meters and WAV files.
 
 The wrappers stay separate workspaces, each with its own lockfile, so the
 NIH-plug Git dependency stays out of the root workspace. Host identities and
@@ -45,7 +46,7 @@ python3 -m unittest discover -s scripts/tests -v
 ```
 
 Products: `rivet`, `patina`, `anvil`, `crucible`, `lathe`, `temper`, `weld`,
-`knurl`, `planish`, `braze`, `quench`.
+`knurl`, `planish`, `braze`, `quench`, `ballast`.
 
 `check-plugin.py` runs formatting, tests and clippy for one product's packages
 and its wrapper, without compiling the other products. Run it for every product
@@ -147,6 +148,7 @@ identify plugins by CLAP ID, so the vendor name does not affect saved projects.
 | Planish | (new) | `io.narl.bass-foundry.planish` |
 | Braze | (new) | `io.narl.bass-foundry.braze` |
 | Quench | (new) | `io.narl.bass-foundry.quench` |
+| Ballast | (new) | `io.narl.bass-foundry.ballast` |
 
 CLAP IDs use the form `io.narl.bass-foundry.<product>`. Builds tagged before
 this scheme used `io.storyboard.*` IDs; hosts treat the new IDs as different