Issue: Anthropic plugin ignores file attachments (images, PDFs)

Issue: Anthropic plugin ignores file attachments (images, PDFs): a task in LegoFlow-SWE (Harbor dataset). Description: When using the Anthropic plugin in Fabric with a command that includes an attachment (e.g., fabric --attachment resume.pdf -m claude-opus-4-5 'What is this?' ), the attachment…

The task

**Description:** When using the Anthropic plugin in Fabric with a command that includes an attachment (e.g., `fabric --attachment resume.pdf -m claude-opus-4-5 'What is this?'`), the attachment content is not sent to the Anthropic API. The model only receives the text prompt and does not see the attached file, making…

Part of Lego-X/LegoFlow-SWE.