Fix lint errors (import ordering), resolve FileReadStream type mismatch
for mobile's Blob-based readStream, move tests from src/__tests__ to
top-level test/ directory matching web/server conventions, and add tests
for emoji, message, node, radar utils plus an in-memory error log for
debugging experimental builds.
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
