policy-catalogue: add Zig / Zig Software Foundation entry

[sjh9714]

Summary

Adds policy-catalogue/zig.md, closing #9. Note on sourcing: there is no CONTRIBUTING.md in ziglang/zig and the old wiki page is now a redirect — the operative text lives in the Code of Conduct under "Strict No LLM / No AI Policy", surfaced in-repo only as a one-line link in .forgejo/ISSUE_TEMPLATE/config.yml ("Please do not use GitHub Copilot or any other LLM to write an issue").

This is the strictest policy in the catalogue and the only one that reaches upstream of the artifact — it bars using an LLM to brainstorm even when you write the prose yourself, and bars acting on chatbot advice when commenting. Two more things worth your attention: it bans LLM translation, which four other catalogued policies explicitly permit or encourage, resolving the accessibility question the opposite way ("post in your native language and rely on others to have their own translation tools") — so a translations stance value can't be read as a proxy for inclusiveness. And "No talking about use of chatbot/LLM services" is a speech rule, not a contribution rule, which nothing else in the corpus has.

Also relevant to the canonical_url question raised in the Home Assistant entry, from the opposite direction: here the repository holds only a pointer and the policy lives on the website, so an agent reading the repo would find the link but not the text.

AI disclosure (required — we dogfood our own standard)

• AI-assisted — tool and role: drafted by Claude (Claude Code) working under my direction. Every verbatim excerpt was verified programmatically against the pinned source before submission (26 string checks across this batch of five entries, all passing).

Attestations (required)

• understands-change — I can explain every part of this entry and the sources behind it.
• reviewed-output — reviewed before submission. Being precise about the mechanism rather than just ticking: I reviewed a structured walkthrough of the entry plus the verification output confirming each quoted string exists at the pinned source, rather than reading the rendered diff line-by-line.
• ran-tests — N/A (prose only).

Type of contribution

• Policy-catalogue entry (single file in policy-catalogue/)

I've left policy-catalogue/README.md untouched across this batch — #21 already edits that table and several PRs touching the same rows would conflict. Happy to send one follow-up PR updating the count and all rows once merge order is settled.

Maintainership disclosure: I maintain MergeWarden, a checker in the layer-3 space discussed in #20/#22. This entry documents the project's policy only and makes no claim about any tool.