The impact graph only recognises Cargo, npm and Python projects

[Muawiya-contact]

The impact graph knows three kinds of project:

const PROJECTS: &[(&str, ProjectKind, &[&str])] = &[
    ("cargo.toml",     ProjectKind::Cargo,  &["target"]),
    ("package.json",   ProjectKind::Npm,    &["node_modules"]),
    ("pyproject.toml", ProjectKind::Python, &[".venv", "venv"]),
];

Which means a Go, Java, Ruby or PHP project's build output looks
abandoned to Diskern even when the project is live — it gets the same
verdict as a directory nobody has touched in two years, which is exactly
the distinction the graph exists to make.

Candidates, each a line in that table plus a store name:

Marker	Store
go.mod	vendor
pom.xml	target
build.gradle, build.gradle.kts	build, .gradle
Gemfile	vendor/bundle
composer.json	vendor
pubspec.yaml	.dart_tool, build

Note target and vendor are shared between ecosystems, which is fine —
STORE_NAMES is a flat list and the marker decides who references what.

Worth checking as you add each one: graph.rs has tests using synthetic
paths, so a new kind needs no filesystem, just a from_entries case
asserting the store comes back referenced.

crates/diskern-core/src/graph.rs:24