- Add gc_export_importer.go: reads pre-compiled type data from Go build
  cache instead of parsing source, dramatically faster for large deps
- Type resolver now tries gcexportdata first, falls back to source importer
- Optional DINGO_PROFILE=1 env var for timing diagnostics
- Value enum formatting cleanup

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>