feat(plugin-kit): scaffold @punktfunk/plugin-kit + phase-0 spikes

Two spikes validating the riskiest seams of the plugin-kit design before
implementation:

- HttpApi (effect/unstable/httpapi) served on Bun behind the SDK's
  servePluginUi using ONLY effect-core layers (Etag.layerWeak, Path.layer,
  HttpPlatform.layer + FileSystem.layerNoop) — no platform package. Auth,
  schema validation, and static fallthrough all verified end-to-end.
- Browser client prefix strategy for the console proxy: both
  transformClient+prependUrl AND baseUrl preserve the /plugin-ui/<id>
  path prefix. Nested Schema.withDecodingDefaultKey defaults confirmed
  (Effect-valued defaults; encodingStrategy "omit" restores raw shape
  on encode).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

plugin-kit/package.json

@@ -0,0 +1,58 @@
+{
+	"name": "@punktfunk/plugin-kit",
+	"version": "0.1.0",
+	"description": "Effect-based framework for punktfunk plugins: lifecycle runtime, config/state, sync engine, UI serving, CLI scaffold, and browser helpers.",
+	"type": "module",
+	"license": "MIT OR Apache-2.0",
+	"homepage": "https://git.unom.io/unom/punktfunk/src/branch/main/plugin-kit",
+	"repository": {
+		"type": "git",
+		"url": "https://git.unom.io/unom/punktfunk.git",
+		"directory": "plugin-kit"
+	},
+	"bugs": {
+		"url": "https://git.unom.io/unom/punktfunk/issues"
+	},
+	"keywords": ["punktfunk", "plugin", "framework", "effect"],
+	"main": "./dist/index.js",
+	"types": "./dist/index.d.ts",
+	"exports": {
+		".": {
+			"types": "./dist/index.d.ts",
+			"default": "./dist/index.js"
+		},
+		"./react": {
+			"types": "./dist/react/index.d.ts",
+			"default": "./dist/react/index.js"
+		},
+		"./theme.css": "./dist/theme.css"
+	},
+	"files": ["dist", "README.md"],
+	"publishConfig": {
+		"registry": "https://git.unom.io/api/packages/unom/npm/"
+	},
+	"scripts": {
+		"typecheck": "tsc --noEmit",
+		"build": "tsc -p tsconfig.build.json && cp src/theme.css dist/theme.css",
+		"test": "bun test",
+		"prepublishOnly": "bun run build"
+	},
+	"peerDependencies": {
+		"effect": "^4.0.0-beta.98",
+		"@punktfunk/host": "^0.1.1",
+		"react": ">=19",
+		"@effect/atom-react": "^4.0.0-beta.99",
+		"@unom/ui": ">=0.9.0"
+	},
+	"peerDependenciesMeta": {
+		"react": { "optional": true },
+		"@effect/atom-react": { "optional": true },
+		"@unom/ui": { "optional": true }
+	},
+	"devDependencies": {
+		"effect": "4.0.0-beta.99",
+		"@punktfunk/host": "file:../sdk",
+		"@types/bun": "^1.3.0",
+		"typescript": "^5.9.3"
+	}
+}