fix(sandbox): point image downloads at the codev storage prefix

The bucket moved the sandbox images from codev-code/sandbox to
codev/sandbox, and the old prefix now returns 403 — so every sandbox
create failed at the manifest fetch. Repoint the base URL; the manifest
URL and every asset URL the build script generates follow from it.

Verified against the live bucket: the manifest and all four artifacts
resolve at the new prefix with the expected sizes.

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

Author: quickbeard

packages/codev-sandbox/src/const.ts

@@ -3,7 +3,7 @@
 // user-visible at download time.
 const STORAGE_BASE = atob("aHR0cHM6Ly9uZXRtaW5kLnZpZXR0ZWwudm4vY29kZXYtc3RvcmFnZQ==")
 
-export const SANDBOX_IMAGES_BASE_URL = `${STORAGE_BASE}/codev-code/sandbox`
+export const SANDBOX_IMAGES_BASE_URL = `${STORAGE_BASE}/codev/sandbox`
 
 export const SANDBOX_MANIFEST_URL = `${SANDBOX_IMAGES_BASE_URL}/manifest.json`