Persist cookies and localStorage in browser profiles

[danwalmsley]

Summary

• persist future-expiring cookies and per-origin localStorage under the existing host-selected directory and partition identity
• keep session cookies and sessionStorage ephemeral while preserving cookie metadata, ordering, quota, and storage-event behavior
• add atomic coalesced checkpoints, schema validation, corruption recovery, process locking, bounded clear-data APIs, and IndexedDB-aware all-site-data clearing
• document profile lifecycle, shutdown budget, permissions, threat model, and IndexedDB composition
• add restart, cross-process, interrupted-write, corruption, concurrent-open, clear-data, quota, event-delivery, and repeated lifecycle contracts

Validation

• built webscene_native_engine_tests and webscene_profile_storage_tests on macOS arm64
• ctest -R ^webscene_profile_storage_tests$ --output-on-failure
• WEBSCENE_NATIVE_ENGINE_TEST_FILTER=response-header-cookie webscene_native_engine_tests
• WEBSCENE_NATIVE_ENGINE_TEST_FILTER=web-storage webscene_native_engine_tests
• git diff --check

Related work

This composes with the IndexedDB partition model from #56 / #94 and the cookie propagation work from #188 and #210. It does not duplicate IndexedDB transactions.

Remaining qualification evidence

Linux x64, Windows x64, Native AOT/relocated SDK, and a manual Spotify restart confirmation still need to run in their dedicated environments. The SpotifyCatalog sample named by the issue is not present on current main; the companion AppScene PR wires the maintained JavaScript host sample and generic SDK API instead.

Addresses #437