feat(logo-creator): add optional Atlas Cloud provider

[binyangzhu000-sudo]

Description

Adds Atlas Cloud as an optional image-generation provider for logo-creator while preserving the existing Nano Banana path as the default.

Type of Change

• New feature (non-breaking change which adds functionality)
• Enhancement to existing skill

Changes Made

• Add a standard-library Atlas runner that validates the live model catalog and model-specific schema before every request.
• Require an explicit generation confirmation, submit exactly one potentially billable POST, bound prediction GET polling, and validate downloaded image artifacts.
• Document the provider-selection and dry-run workflow.
• Add focused tests and update the skill's plugin/marketplace metadata to 1.1.0.

Affected Skills

• logo-creator

Testing Done

• python3 -m unittest discover -s skills/logo-creator/tests -v
• python3 -m py_compile skills/logo-creator/scripts/generate_atlas.py skills/logo-creator/tests/test_generate_atlas.py
• Live, non-billable catalog/schema dry-run against google/nano-banana-2/text-to-image
• Local npx skills add installation for logo-creator on Codex
• jq empty for all changed JSON manifests
• git diff --check

No generation POST was made during validation.