feat: Add Line plugin (#1630)

* feat: add LINE plugin (#1630) (thanks @plum-dawg)

* feat: complete LINE plugin (#1630) (thanks @plum-dawg)

* chore: drop line plugin node_modules (#1630) (thanks @plum-dawg)

* test: mock /context report in commands test (#1630) (thanks @plum-dawg)

* test: limit macOS CI workers to avoid OOM (#1630) (thanks @plum-dawg)

* test: reduce macOS CI vitest workers (#1630) (thanks @plum-dawg)

---------

Co-authored-by: Peter Steinberger <steipete@gmail.com>

src/gateway/server-plugins.test.ts

@@ -18,6 +18,7 @@ const createRegistry = (diagnostics: PluginDiagnostic[]): PluginRegistry => ({
   providers: [],
   gatewayHandlers: {},
   httpHandlers: [],
+  httpRoutes: [],
   cliRegistrars: [],
   services: [],
   diagnostics,