feat: add a sandbox image-viewing tool for agent vision tasks

[QueryPlanner]

Summary

Add an agent-accessible tool for viewing image files stored in the sandbox.

The tool should let the agent provide a sandbox image path and receive the image through a model-compatible visual input channel. This gives the agent a reliable way to inspect images that arrived as Telegram files/documents or were restored from attachment storage.

Motivating use case

Send multiple images to the Black Key Telegram bot and ask:

create 2 collage - randomly select 6 pictures in a colloege

The agent should be able to inspect the individual images stored in the sandbox, choose the requested images, and create the collages.

Proposed behavior

• Add a tool such as sandbox_view_image.
• Accept a sandbox-relative image path or an attachment reference.
• Validate that the target is an allowed sandbox file.
• Support common image formats and MIME types.
• Return the image in a model-compatible visual response, not only metadata or a text path.
• Preserve individual image boundaries when viewing multiple images.
• Return a clear, bounded error for missing, invalid, or unsupported files.

Security and reliability requirements

• Restrict reads to the active sandbox and approved attachment locations.
• Do not allow path traversal or arbitrary host filesystem access.
• Enforce reasonable file-size and image-dimension limits.
• Keep the tool read-only.
• Ensure the tool works after attachment restoration or sandbox reconnect when the file is available.

Acceptance criteria

• An agent can call the tool with an image stored in the sandbox and receive a visual representation it can inspect.
• The tool supports images uploaded to Telegram as files/documents.
• Multiple images can be viewed independently for selection and collage operations.
• Missing, unsupported, oversized, and invalid images produce actionable errors.
• Path validation prevents access outside the active sandbox.
• Unit and integration tests cover single-image viewing, multiple-image viewing, restored attachments, and invalid paths.
• The tool is documented and registered in the agent's available tool set.