Handle attached Docker run output

[X1pheR]

Summary

Handle the Docker SDK return type for run_container(detach=false) instead of passing attached command output to docker_to_dict().

Problem

docker.containers.run(..., detach=False) returns command output bytes. The current tool always calls docker_to_dict() on the result, which only supports Docker model objects, so attached execution fails during result conversion even when the command itself succeeded.

Change

• Preserve the existing Docker-object response for detached execution.
• Return attached command output as structured {mode: "attached", output: ...} data.
• Decode invalid UTF-8 using replacement rather than failing result serialization.
• Reject unexpected return types explicitly.

This PR intentionally does not add output-size policy; it only fixes the Docker SDK type contract.

Validation

• ruff check src tests
• pytest -q: 6 passed
• Live MCP validation with alpine:latest and detach=false returned the expected command output successfully.