Improve the first-run CLI handoff

[fly1d]

Why

The network-free demo completes in seconds, but it sent new users to a 103-line Doctor help screen instead of the next real check. The terminal path also had no direct route for help or feedback, and shareable validation output required scanning the evidence table to learn whether it passed.

What changed

• Point demo users to a copyable, read-only repomin doctor command for the generated source.
• Link root help and demo output directly to SUPPORT.md.
• Lead Markdown validation with a plain-language result, fingerprint status, and before/after file count.
• Record the behavior in the Unreleased changelog while keeping the README example accurate for the pinned dev11 wheel.

No reducer, oracle, backend, report schema, or network behavior changed.

Verification

• python -m unittest discover -s tests -q -> 764 passed, 4 skipped
• python benchmarks/run_offline.py -> 16 passed
• python scripts/check_quickstart.py -> passed
• python scripts/check_docs.py -> 48 Markdown files passed
• python -m ruff check . and git diff --check -> passed
• fresh wheel and virtual environment -> demo, copied Doctor command, validation summary, and support link passed

Disclosure

Prepared with material OpenAI Codex assistance and maintainer review. This changes local CLI guidance and report presentation only.