feat: add Lathe harmonic EQ and Temper tracked distortion

Lathe places EQ bands on harmonics 1-32 of the played note, so a cut on
harmonic 3 stays on harmonic 3 on every note. Temper normalises each
note's level before an oversampled shaper and tunes its floor, push and
bright filters to the note, so every note distorts the same.

The note tracker moves from Anvil into common-dsp, together with a
state-variable filter, 4x oversampler and harmonic meter. Anvil's
behaviour and editor render are unchanged.

docs/ideas.md collects all plugin ideas and their status.

docs/development.md

@@ -27,6 +27,8 @@ python scripts/check-plugin.py --plugin rivet
 python scripts/check-plugin.py --plugin patina
 python scripts/check-plugin.py --plugin anvil
 python scripts/check-plugin.py --plugin crucible
+python scripts/check-plugin.py --plugin lathe
+python scripts/check-plugin.py --plugin temper
 python -m unittest discover -s scripts/tests -v
 ```
 
@@ -49,6 +51,8 @@ python scripts/build-plugin.py --plugin rivet --target x86_64-pc-windows-gnu
 python scripts/build-plugin.py --plugin patina --target x86_64-pc-windows-gnu
 python scripts/build-plugin.py --plugin anvil --target x86_64-pc-windows-gnu
 python scripts/build-plugin.py --plugin crucible --target x86_64-pc-windows-gnu
+python scripts/build-plugin.py --plugin lathe --target x86_64-pc-windows-gnu
+python scripts/build-plugin.py --plugin temper --target x86_64-pc-windows-gnu
 python scripts/package-windows.py
 python scripts/package-windows.py --plugin rivet
 python scripts/package-windows.py --plugin patina
@@ -77,6 +81,8 @@ cargo run --manifest-path tools/editor-check/Cargo.toml -- /tmp/patina.png --plu
 cargo run --manifest-path tools/editor-check/Cargo.toml -- /tmp/patina-compact.png --plugin patina --compact
 cargo run --manifest-path tools/editor-check/Cargo.toml -- /tmp/anvil.png --plugin anvil
 cargo run --manifest-path tools/editor-check/Cargo.toml -- /tmp/crucible.png --plugin crucible
+cargo run --manifest-path tools/editor-check/Cargo.toml -- /tmp/lathe.png --plugin lathe
+cargo run --manifest-path tools/editor-check/Cargo.toml -- /tmp/temper.png --plugin temper
 ```
 
 Patina also accepts `--silent`, `--delta`, and `--bypass` as render fixtures.