fix(server): gate cost/log endpoints against cross-site requests and ship a full CSP

The cost-bearing endpoints (/api/realtime/token, /api/openai/hud-summary,
/api/google/nearby-places) and the voice debug log refuse cross-site browser
requests: a foreign or opaque Origin, a Sec-Fetch-Site other than
same-origin/none, or proxy forwarding headers. Loopback tools without an
Origin and the LAN opt-in keep working. The dev and preview servers send one
shared Content-Security-Policy, and embed-mode framing rewrites only the
frame-ancestors directive of it.

Salvaged from #242 onto current main.

Co-authored-by: Sameh Khamis <[email protected]>
Co-Authored-By: Claude Opus 5.5 (1M context) <[email protected]>

src/tooling/viteBuild.test.mjs

@@ -1,7 +1,7 @@
 import test from 'node:test';
 import assert from 'node:assert/strict';
 import { readFileSync } from 'node:fs';
-import { createBrowserViteConfig } from '../../build/vite.js';
+import { BROWSER_CSP, createBrowserViteConfig } from '../../build/vite.js';
 import standaloneConfig, * as compatibility from '../../vite.config.js';
 import * as providers from '../../server/providers/local.js';
 
@@ -23,10 +23,18 @@ test('explicit build inputs preserve browser-only defines, plugin order and loop
   assert.ok(config.server.fs.deny.includes('**/ENVIRONMENT'));
   assert.ok(config.server.fs.deny.includes('.env.*'));
   assert.equal(config.server.headers['X-Frame-Options'], 'DENY');
-  assert.equal(
-    config.server.headers['Content-Security-Policy'],
+  const csp = config.server.headers['Content-Security-Policy'];
+  assert.equal(csp, BROWSER_CSP);
+  for (const directive of [
+    "script-src 'self' 'unsafe-eval' blob:",
+    "object-src 'none'",
+    "base-uri 'self'",
     "frame-ancestors 'none'",
-  );
+  ]) {
+    assert.ok(csp.includes(directive), directive);
+  }
+  assert.ok(!csp.includes("script-src 'self' 'unsafe-inline'"));
+  assert.deepEqual(config.preview.headers, config.server.headers);
   assert.deepEqual(config.define, {
     'import.meta.env.GOOGLE_MAPS_API_KEY': '"browser-fixture"',
     'import.meta.env.CESIUM_ION_TOKEN': '"ion-fixture"',
@@ -127,6 +135,22 @@ test('only embed-mode documents may be framed, and only by the allowed ancestors
   anywhere.setHeader('X-Frame-Options', 'DENY');
   anywhere.setHeader('Content-Security-Policy', "frame-ancestors 'none'");
   assert.deepEqual(Object.fromEntries(anywhere.headers), {});
+  // A full policy keeps its other directives; only the framing rule changes.
+  const full = "default-src 'self'; script-src 'self'; frame-ancestors 'none'";
+  const embeddedFull = response();
+  middleware({ url: '/?embed=1' }, embeddedFull, () => {});
+  embeddedFull.setHeader('Content-Security-Policy', full);
+  assert.equal(
+    embeddedFull.headers.get('content-security-policy'),
+    "default-src 'self'; script-src 'self'; frame-ancestors https://a.example",
+  );
+  const anywhereFull = response();
+  open({ url: '/?embed=1' }, anywhereFull, () => {});
+  anywhereFull.setHeader('Content-Security-Policy', full);
+  assert.equal(
+    anywhereFull.headers.get('content-security-policy'),
+    "default-src 'self'; script-src 'self'",
+  );
   const normal = response();
   middleware({ url: '/' }, normal, () => {});
   normal.setHeader('X-Frame-Options', 'DENY');