chore: prepare v1.13.0 release

[typelicious]

Summary

• bump the runtime and package version to v1.13.0
• document the Anthropic bridge as an opt-in release line in the changelog, releases doc, and roadmap
• set the next roadmap focus back to a more live provider catalog after the bridge release

Validation

• rtk ruff check faigate/init.py tests/test_main_cli.py tests/test_release_scripts.py
• env PYTHONPATH=. ./.venv-check-313/bin/pytest -q tests/test_main_cli.py tests/test_release_scripts.py
• python3 scripts/faigate-release --version 1.13.0 --dry-run --allow-dirty --skip-verify