feat: add chains scaffold and loot contract

[TacoRocket]

Summary

• split loot output from full json output and cap loot to top-ranked targets
• add internal chains scaffold models, registry, and validation tests
• expose chains as a planned help-visible grouped surface and remove stale wiki seed docs

Validation

• python3 -m pytest tests/test_help.py tests/test_chain_scaffold.py tests/test_output_writer.py tests/test_cli_smoke.py -q
• python3 -m ruff check src/azurefox/help.py src/azurefox/cli.py src/azurefox/chains src/azurefox/models/chains.py tests/test_help.py tests/test_chain_scaffold.py src/azurefox/output/writer.py tests/test_output_writer.py tests/test_cli_smoke.py README.md docs/output-contracts.md
• pre-push guardrail: 213 passed, 2 deselected