Add StartOS 0.4 package scaffold (manifest, main, interfaces, 2 actions)

- package/Makefile + s9pk.mk + package.json + tsconfig.json
- startos/manifest: dockerBuild source pointing at ../image/Dockerfile
- startos/main: reads /data/config.yaml reactively, passes env vars to container
- startos/interfaces: binds port 9999 as HTTP UI
- startos/actions: showPublicKey (read /data/ssh/id_ed25519.pub), configureSparks
- TS + JS bundle compile clean (tsc --noEmit, ncc build)

package/startos/fileModels/sparkConfig.yaml.ts

@@ -0,0 +1,17 @@
+import { FileHelper } from '@start9labs/start-sdk'
+import { z } from 'zod'
+import { sdk } from '../sdk'
+
+export const sparkConfigSchema = z.object({
+  spark1_host: z.string().catch(''),
+  spark1_user: z.string().catch('<spark-user>'),
+  spark2_host: z.string().catch(''),
+  spark2_user: z.string().catch('<spark-user>'),
+})
+
+export type SparkConfig = z.infer<typeof sparkConfigSchema>
+
+export const sparkConfigYaml = FileHelper.yaml(
+  { base: sdk.volumes.main, subpath: 'config.yaml' },
+  sparkConfigSchema,
+)