RootResolver

Resolves the CONSUMING APPLICATION's filesystem root — the directory a consuming app runs `npm install` from, and where `node_modules/@milpa/design` therefore lands — the one piece of topology {@see MilpaDesign} needs and cannot safely assume about its own location. Ported from `milpa/devtools`' `Milpa\DevTools\Support\RootResolver` (same resolution order, same failure mode) rather than depended on, to keep this package's own dependency graph free of devtools' Doctrine coupling. Prior to this class, `MilpaDesign` computed its answer as `dirname(__DIR__, 2)` from its own file — correct only when this package's `src/Support/` happens to sit exactly two levels under the consuming application's root, which is true in this monorepo's dev layout but false the moment `milpa/live-web` is Composer-vendored (`vendor/milpa/live-web/...`, any install depth): the walk lands under `vendor/`, not at the consuming app's root, so `node_modules/@milpa/design` is looked for in the wrong place and the failure is silent — a same-named directory could even exist there by coincidence. Resolution order (first hit wins): 1. an explicit root passed to the constructor — host wiring always wins (e.g. a container binding the app root once from a known-good source, or a test fixture); 2. `Composer\InstalledVersions::getRootPackage()['install_path']` — the Composer-canonical answer to "where is the application that required me", correct regardless of install depth or path-repo vs. registry install, valid the instant Composer's generated autoloader is on the include path (which it always is for any Composer-managed PHP process — this is not an optional dependency, see `composer-runtime-api` in `composer.json`); 3. walk up from `getcwd()` looking for the nearest ancestor `composer.json` — a last-resort fallback for the pathological case where Composer's own runtime API is unavailable (e.g. this package used outside a Composer-managed process entirely). Throws {@see RootNotFoundException} instead of returning a plausible-looking wrong path when none of the three resolves — callers get an honest, loud failure.

public function __construct(?string $explicitRoot = null):

Parameters

public function resolve(): string

Resolves the consuming application's root directory per the three-tier order documented above.