v0.8.9: e2e tests — WebSocket, resource resolution, serve integration

New test files:
- internal/ws/ws_test.go — 13 tests for RFC 6455 WebSocket:
  upgrade, text/binary/empty/large/very-large frames,
  concurrent writes, close, error cases
- internal/resource/resource_test.go — 24 tests for @ reference
  parsing, replacement, file resolver (search, load, traversal
  prevention, symlink blocking, .git exclusion), session
  resolver, registry routing
- cmd/kode/serve_test.go — 10 integration tests for the full
  HTTP server: UI serving, 404, session list API, resource
  search API, WebSocket upgrade, prompt flow, invalid messages,
  concurrent prompts

Also fixed: walkAndMatch recursive file search (was matching all
files due to ** glob parsing), Dial URL path support, skipDir
integration in filepath.Walk.

All tests pass. 0 flaky tests.

Author: jkyberneees