v0.29.0 the configuration engine, and lw --schema

AGENTS.md

@@ -79,6 +79,10 @@ change touches.
   `config.Decode`, which applies the defaults, rules and pure checks and
   refuses unknown keys at any depth; they keep only I/O. Rules that read
   nothing belong in a `Check` method, so `ValidateConfig` sees them offline.
+- `internal/compose` is the engine `lw --tui` and the website's WebAssembly
+  share: it edits pipelines and writes the command line, environment and file
+  forms, each loading back to the same pipelines; it reads no file and links
+  no TLS, HTTP or terminal code (its test runs `go list -deps`).
 - `cmd/lw/cli.go` owns the command line: lw's own flags, and the commands
   table whose groups (`auth`, `tls`, `preset`, `config`) share one flag
   mechanism; `config.Load` takes the parsed `config.Args`. Presets are rows of