Scaffold NIH-plug project: full-band gain VST3/CLAP with one-slider egui GUI

Sets up the Rust/NIH-plug build (pinned to nih-plug rev f36931f) producing
VST3 and CLAP bundles via 'cargo xtask bundle'. Implements the first landmark:
a full-band gain plugin with a single egui ParamSlider.

- Cargo workspace + xtask bundler, .cargo alias, bundler.toml
- src/lib.rs: Codename206 plugin (gain param, egui editor)
- deploy.ps1/.bat: build + install to system VST3/CLAP folders (real copy,
  not a junction, for FL Studio); -User flag for a no-admin dev loop
- LICENSE: GPL-3.0 (required by NIH-plug's VST3 bindings)
- README: corrected architecture for the 'All' aggregate channel (4th comp/lim
  stack on the summed bands; all-bands-bypassed = simple full-band comp)
- .gitignore excludes /target and the local nih-plug + _template reference clones

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

deploy.bat

@@ -0,0 +1,5 @@
+@echo off
+REM Double-click wrapper for deploy.ps1 (build + install to system VST3/CLAP folders).
+REM Pass-through args, e.g.:  deploy.bat -User   /   deploy.bat -SkipBuild
+powershell -NoProfile -ExecutionPolicy Bypass -File "%~dp0deploy.ps1" %*
+pause