Binary file data (PPTX, PDF, images) returned by one tool and echoed by
the model as a base64 argument to another tool drifts by a few characters,
invalidating the base64 and corrupting the resulting file.
Tools can now return a FileArtifact instead of a base64 string. The agent
executor stores the bytes out-of-band (execution-scoped, TTL-backed) and
shows the model a short, namespaced `crewai+file://` handle, expanding it
back to exact base64 just before the consuming tool runs. Wired into the
native (default AgentExecutor + legacy) and ReAct execution paths with
per-run cleanup.
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