#133 docs: remove private downstream project references

This fork is public, so it shouldn't name a private downstream project.

1. Reverts #132, which imported fork evidence from a private repository. The evidence goes back to that repository.
2. Rewords the older mentions in two tests, four benchmark and design docs and one plan. The repository name, URL, home paths and commit links now read as "a private downstream project" or "a private fixture". The synthetic test fixture uses neutral names.
3. Adds one line to AGENTS.md: never name private projects, their repositories, source paths or home directories here.

After this change, git grep -iE 'espn|chrome-ext|/home/bompus' finds nothing. The earlier content stays in git history and on the #132 page; purging it would mean rewriting fork/consolidated, which we decided against.

Checks: vitest literal-capture and explore-elided-symbol-names pass (16/16), and check-agent-docs passes (AGENTS.md 32163/32768 bytes).