Update to Bun 1.4

[astrovm]

Summary

• update the project and CI runtime pins from Bun 1.3.14 to 1.4.0
• update @types/bun and refresh compatible lockfile dependencies
• make the offline-update timer test wait for the observable registration instead of one event-loop turn

Validation

• bun install --frozen-lockfile
• bun run quality
• bun run test (163 passed)
• bun run build --revision HEAD
• git diff --check