Docs: verify the Docker and pre-commit adoption paths

[ChelseaKR]

Goal

Test the Docker and pre-commit adoption paths from clean projects and correct
any missing setup step.

Test matrix

1. Run the published container against the synthetic sample feed.
2. Add the documented pre-commit hook to a temporary repository.
3. Confirm a valid fixture passes.
4. Confirm a deliberately invalid fixture blocks the hook.

Do not use or commit real agency operational data.

Done when

• Record platform, container runtime, and tods-validate version.
• Confirm the expected exit codes for passing and failing fixtures.
• Identify any path, volume, version pin, or hook-stage ambiguity.
• Submit a focused README or getting-started correction if needed.

The task is complete when both documented paths are verified, even if no code
change is required.