feat: add solutions command

[jeff-schnitter]

Summary

• Adds cortex solutions subcommand with list, info, and install commands
• Solutions are bundled in the CLI package at cortexapps_cli/solutions/<tag>/ and resolved via importlib.resources
• Each solution is a Cortex backup-format directory with a README.md (YAML frontmatter + ASCII diagram)
• install delegates to backup import_tenant; shows README after install (suppress with --no-info)
• Includes github-starter bundle: GitHub Readiness scorecard
• Auth bypass in global_callback for solutions group; install builds its own client

Commands

cortex solutions list
cortex solutions info -s <tag>
cortex solutions install -s <tag> [--force] [--no-info]

Test plan

• cortex solutions list renders table with github-starter
• cortex solutions info -s github-starter renders README with diagram
• cortex solutions info -s bad-tag exits 1 with helpful error
• cortex solutions install -s github-starter imports scorecard and shows README
• cortex solutions install -s github-starter --no-info imports without README
• Unit tests: pytest tests/test_solutions.py — 7 passed, 1 skipped

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