feat(web): migrate OAuth store to shared /store API (RemoteOAuthStorage parity) (closes #1548)

Migrate the web client's OAuth storage from BrowserOAuthStorage
(sessionStorage) to RemoteOAuthStorage, which POSTs through the backend's
/api/storage/oauth route to ~/.mcp-inspector/storage/oauth.json (mode 0600).
A credential obtained in the browser is now the same blob the TUI/CLI read
on the same host, giving web ⇄ TUI ⇄ CLI parity (Wave 1 of #1579).

Core (shared with TUI/CLI):
- OAuthStorageBase now drives a single async hydration (`ready()`,
  `getHydrationError()`); every post-redirect read (getClientInformation,
  getTokens, getCodeVerifier, getServerMetadata, getIdpSession) and every
  save awaits it so a late hydration merge cannot clobber a fresh write.
  getCodeVerifier/getServerMetadata become async; the store is created with
  skipHydration:true so there is no auto-hydration to race the explicit one.
- store.ts adds normalizeServerUrl so a token saved under
  https://Example.com/mcp is found when the CLI asks for
  https://example.com/mcp/; getServerState falls back to the raw key.
- remote-storage adapter POSTs with keepalive so the write survives the
  OAuth authorize redirect, surfaces swallowed persist failures, and gives
  richer read/write error messages.
- generateOAuthState throws instead of silently degrading to Math.random.
- NodeOAuthStorage honors MCP_INSPECTOR_OAUTH_STATE_PATH for isolated
  fixtures. Provider codeVerifier()/getServerMetadata() + the EMA idpOidc and
  connection-state readers await the now-async storage.

Web:
- environmentFactory + a new shared lib/remoteOAuthStorage accessor
  (memoized per {baseUrl, authToken}) wire RemoteOAuthStorage into the
  connection path, the EMA IdP hook, and the per-server "clear OAuth" action
  so all three share one in-memory view of oauth.json.

Tests: async-hydration + normalizeServerUrl suite, keepalive/error-path
coverage, and the sync→async migration across existing storage/provider/EMA
tests. Web validate + coverage gate + integration suite green; CLI/TUI/
launcher validate green.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01S3fTN8H3R8YV4yUGvZjYnX

core/auth/utils.ts

@@ -50,20 +50,17 @@ export const parseOAuthCallbackParams = (location: string): CallbackParams => {
  * @returns A random state for the OAuth 2.0 flow.
  */
 export const generateOAuthState = (): string => {
-  // Generate a random state
-  const array = new Uint8Array(32);
-
-  // Use crypto.getRandomValues (available in both browser and Node.js)
-  if (typeof crypto !== "undefined" && crypto.getRandomValues) {
-    crypto.getRandomValues(array);
-  } else {
-    // Fallback for environments without crypto.getRandomValues
-    // This should not happen in modern environments
-    for (let i = 0; i < array.length; i++) {
-      array[i] = Math.floor(Math.random() * 256);
-    }
+  // OAuth state is a CSRF token — it MUST be unpredictable. crypto.getRandomValues
+  // is available in every supported runtime (browsers, Node ≥15); if it's somehow
+  // missing, fail loudly rather than silently degrading to Math.random (whose
+  // output is predictable from a small amount of observed state).
+  if (typeof crypto === "undefined" || !crypto.getRandomValues) {
+    throw new Error(
+      "crypto.getRandomValues is not available; refusing to generate an OAuth state with a non-cryptographic RNG.",
+    );
   }
-
+  const array = new Uint8Array(32);
+  crypto.getRandomValues(array);
   return Array.from(array, (byte) => byte.toString(16).padStart(2, "0")).join(
     "",
   );