release: RecallBase v0.1.8

[DarinRowe]

Summary

• bump RecallBase package and agent integration metadata to 0.1.8
• publish Chromium fork discovery, explicit fallback registration, and Firefox channel reporting
• document Windows compiled native-host fixes and cross-platform release coverage

Validation

• bun test (194 passed)
• bun run typecheck
• bun run package:agent-skill:check
• actionlint .github/workflows/*.yml
• stable release packaging for all five CLI targets
• npm packaging for all five CLI targets
• Homebrew cask generation