Add configurable tus chunking and stability fixes

Enable configurable chunked tus uploads and related robustness changes.

- Add AGENT_TUS_CHUNK_SIZE_BYTES env (default 1 MiB, 0 disables chunking) and docs in machinery/.env; ignore machinery/go.work files and set GOWORK=off in VSCode launch to avoid go.work during debugging.
- Implement tusChunkSize() and update uploadVaultResumable to send PATCHes in configurable chunk sizes, checkpoint progress after each chunk, and handle partial failures by refreshing retry budget when progress occurs.
- Change tusPatch to accept an explicit length and return the advanced offset when a PATCH is fully accepted.
- Skip uploads when the recording file no longer exists to avoid infinite retries.
- Add tests exercising chunked uploads, chunking-disabled behavior, and tusChunkSize parsing; extend fakeTus test server to record patch sizes.
- Reduce noisy info logs to debug in AAC transcoder and WebRTC audio processing.

These changes improve resumable upload reliability, allow tuning for proxy/load-balancer limits, and reduce log spam during normal operation.

.gitignore

@@ -14,5 +14,7 @@ machinery/test*
 machinery/init-dev.sh
 machinery/.env.local
 machinery/vendor
+machinery/go.work
+machinery/go.work.sum
 deployments/docker/private-docker-compose.yaml
 video.mp4