Read configured sandbox process logs by ID

[tonywok]

Adds support for fetching configured background process logs using the same interface as adhoc sandbox background processes.

Landing this ahead of landing agent support.

AI Summary

Summary

Adds support for reading configured sandbox background-process logs through their existing logsId.

When the sandbox agent returns a logsId, the CLI:

• Uses the sandbox run ID to request the existing signed logs token from Cloud.
• Streams snapshots from /api/logs/:logsId/download.
• Streams historical and live output from /api/logs/:logsId with --follow.
• Cancels the follow request cleanly on Ctrl-C.
• Escapes log IDs when constructing URLs.

Responses without logsId continue using the existing SSH and file-backed log behavior. If both a log ID and file paths are present, the log ID takes precedence.

Testing

• go fmt ./...
• golangci-lint run ./...
• go test ./...
• go build ./cmd/rwx
• Focused race tests for the changed CLI packages

Also tested end to end with a locally compiled CLI

• Configured log metadata and snapshot
• Historical and live --follow output
• Ctrl-C cancellation
• Log availability after stop
• Stable log ID across restart generations
• Ad hoc file-backed fallback