E-XXXX: Title of Pull Request

resolves 17+ tracked issues across pods/serverless/templates/gpu/datacenter/billing/ssh/doctor/help.
maintains full legacy command compatibility (stderr warnings only, stdout unchanged).
keeps runpodctl as the primary binary; drop-in upgrade for existing users.
expands api coverage with rest-first + graphql fallback and json/yaml output for automation.
improves onboarding with doctor and auto-migration from ~/.runpod.yaml to ~/.runpod/config.toml.
tests: full unit suite + full e2e suite, with e2e covering all cli entrypoints (legacy + new) and cleanup via t.Cleanup.

Test plan:

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