chore: scaffold minimal NIH-plug template

Based on musiikki/codename-206 patterns. Provides a clean, minimal
skeleton for new nih-plug audio plugins:

- Cargo.toml with pinned NIH-plug deps (same rev as codename-206)
- src/lib.rs — skeleton plugin with Params, Plugin impl, CLAP/VST3
- xtask/ — bundler xtask (cargo xtask bundle)
- bundler.toml — placeholder for bundle name
- .cargo/config.toml — xtask alias
- .gitignore — /target, /nih-plug, /_template
- LICENSE — Apache-2.0
- README.md — build and deploy instructions

.gitignore

@@ -1,18 +1,7 @@
-# ---> Rust
-# Generated by Cargo
-# will have compiled files and executables
-debug/
-target/
+/target
 
-# These are backup files generated by rustfmt
-**/*.rs.bk
-
-# MSVC Windows builds of rustc generate these, which store debugging information
-*.pdb
-
-# RustRover
-#  JetBrains specific template is maintained in a separate JetBrains.gitignore that can
-#  be found at https://github.com/github/gitignore/blob/main/Global/JetBrains.gitignore
-#  and can be added to the global gitignore or merged into this file.  For a more nuclear
-#  option (not recommended) you can uncomment the following to ignore the entire idea folder.
-#.idea/
+# Local NIH-plug reference clone ("deluxe kit") and cookiecutter template.
+# Kept out of version control; the build depends on nih-plug via a pinned git rev,
+# not on these working copies. Clone them locally for reading the examples.
+/nih-plug
+/_template