A platform is named once: WarpEngine::Platform

The list of platforms lived on `PlatformLink::SUPPORTED_PLATFORMS` — a model
about links to a platform's website — and was copied around it four times in
the admin (`%w[tic80 ebitengine love c64 godot bevy phaser]`), spelled out in
three apipie descriptions, and turned into a class name by string
interpolation in three services:

    "WarpEngine::Platforms::#{platform.camelize}::Service".constantize

Seven places that had to agree, and nothing that made them.

`WarpEngine::Platform` is now that one place. `Platform.names` is the list,
`Platform.find!("godot")` answers with a value object that knows its `label`,
its `expected_kinds` and its updater `service`, and the constantize is gone —
the registry holds the reference. `PublishService` and `BuildsService` ask it,
the admin selects read `Platform.names`, and
`PlatformLink::SUPPORTED_PLATFORMS` stays as an alias of `Platform::NAMES` so
a host pinned to 0.7 keeps working.

`Software` also defends its own value sets now. It validated neither `status`
nor `platform`, so a mistyped platform only surfaced later, at publish time,
as "Unsupported platform" — after the row existed. And `status` had three
different answers depending on where you looked: the admin offered
development/demo/released/archived, the API documentation claimed
"active, inactive", and the database holds the first four. `Software::STATUSES`
is the list, the inclusion validations enforce both, and the documentation
names the values the database actually has.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

app/controllers/warp_engine/api/software_controller.rb

@@ -39,8 +39,8 @@ module WarpEngine
         property :desc, String, desc: "Short description"
         property :story, String, desc: "Long description / story"
         property :license, String, desc: "License type"
-        property :platform, String, desc: "Platform (tic80, love, ebitengine, c64, godot, bevy, phaser)"
-        property :status, String, desc: "Status (active, inactive)"
+        property :platform, String, desc: "Platform (one of WarpEngine::Platform::NAMES)"
+        property :status, String, desc: "Status (development, demo, released, archived)"
         property :highlighted, :boolean, desc: "Currently highlighted"
         property :imageUrl, String, desc: "Default image URL"
         property :externalLinks, Array, desc: "External links" do