Drop the Heroku generator's dead code and refresh its USAGE

[tricknotes]

Housekeeping across both generators: dead code, a stale USAGE, and a missing spec.

Why

Dead code. HerokuGenerator#app_paths had no callers — neither the generator nor package.json.erb referenced it — so it described a shape of the configuration that nothing depended on.

USAGE drift. It omitted the yarn.lock that identify_as_yarn_project writes for a Yarn project, and named SKIP_EMBER without saying what unsetting it accomplishes, leaving a reader to guess why the command is in the list at all.

No spec. ember:init had no coverage at all, so nothing caught a broken initializer template.

What changed

• Removed EmberCli::HerokuGenerator#app_paths.
• Rewrote lib/generators/ember/heroku/USAGE: lists yarn.lock, explains SKIP_EMBER, and notes that the generator should be re-run when an application is added.
• Added spec/generators/ember/init/init_generator_spec.rb.

No public API changes, so no CHANGELOG entry.

Out of scope

• The generator classes stay in the EmberCli namespace with their explicit namespace "ember:heroku" / namespace "ember:init" calls. Rails' own convention would infer them from lib/generators/ember/... as Ember::*, but that means introducing a new top-level namespace, which is a deliberate call for the maintainer rather than housekeeping.
• ember:init still does not add mount_ember_app to config/routes.rb — the README documents that as a manual step. Changing it alters what the generator does to a project, so it is left for a separate discussion.

Verification

$ bin/rspec spec/generators
6 examples, 0 failures

Rails::Generators.find_by_namespace still resolves ember:heroku → EmberCli::HerokuGenerator and ember:init → EmberCli::InitGenerator.

Full spec/lib also passes here except EmberCli::App#test exits with exit status of 0, which fails on main in this container too — ember test reports Launcher Chrome not found, unrelated to this change.

🤖 Generated with Claude Code

https://claude.ai/code/session_014rAfkAVGVifbaEoTVeT66u