Add initial VibeGuard browser extension

src/inference/model-metadata.ts

@@ -0,0 +1,36 @@
+export interface ModelManifest {
+  source: string;
+  revision: string;
+  architecture: string;
+  labels: {
+    toxic: number;
+    nonToxic: number;
+    names: Record<string, number>;
+  };
+  maxLength: number;
+  quantization: string;
+  runtime: string;
+}
+
+let manifestPromise: Promise<ModelManifest> | undefined;
+
+export function modelBaseUrl(): string {
+  return chrome.runtime.getURL("models/toxicity/");
+}
+
+export function loadModelManifest(): Promise<ModelManifest> {
+  manifestPromise ??= fetch(`${modelBaseUrl()}model-manifest.json`)
+    .then((response) => {
+      if (!response.ok) throw new Error(`VibeGuard model metadata unavailable (${response.status})`);
+      return response.json() as Promise<ModelManifest>;
+    })
+    .then(validateManifest);
+  return manifestPromise;
+}
+
+export function validateManifest(value: ModelManifest): ModelManifest {
+  if (!value || typeof value.source !== "string" || typeof value.revision !== "string") throw new Error("Invalid VibeGuard model manifest");
+  if (!Number.isInteger(value.labels?.toxic) || !Number.isInteger(value.labels?.nonToxic) || value.labels.toxic === value.labels.nonToxic || !value.labels?.names) throw new Error("Model manifest has no binary label mapping");
+  if (!Number.isInteger(value.maxLength) || value.maxLength < 8) throw new Error("Model manifest has an invalid maximum length");
+  return value;
+}