docs: remove the second contributing note and its dead pointers

CONTRIBUTING-AI.md pointed contributors at a CLAUDE.md "checked in and
kept current"; that file is not in the repository, so the pointer and
the twenty references to it in folder READMEs, docs and comments led
nowhere. The note goes; its one lasting rule (whoever commits a change
stands behind it, no real names, no live health figures, no secrets)
moves into CONTRIBUTING.md. The folder READMEs keep their own content
and drop the dead link, and a reference to the unpublished planning
folder goes with it.

The checked-in .mcp.json was a local editor config no workflow reads;
it is untracked and ignored now. The translation tiers are described
as machine-translated first drafts reviewed by the community, and the
list names Russian, which it missed.

docs/CONTRIBUTING-CLIENTS.md

@@ -1,6 +1,6 @@
 # Building a native client against HealthLog
 
-Working notes for anyone building a client app (Android, iOS, CLI, anything else) against the HealthLog server, with or without AI tooling. Everything in here is a rule we actually follow between the server and the iOS app, written down so a second client does not have to rediscover it. Pair it with `CLAUDE.md` (server-side conventions) and `docs/api/openapi.yaml` (the wire contract).
+Working notes for anyone building a client app (Android, iOS, CLI, anything else) against the HealthLog server. Everything in here is a rule we actually follow between the server and the iOS app, written down so a second client does not have to rediscover it. Pair it with [`CONTRIBUTING.md`](../CONTRIBUTING.md) (server-side conventions) and `docs/api/openapi.yaml` (the wire contract).
 
 ## The contract, and where truth lives
 
@@ -43,7 +43,7 @@ The corollary: if a resolved value you need is missing from a payload, the fix i
 
 ## Ground rules for the repo itself
 
-The voice-and-privacy rules from `CLAUDE.md` apply to any repo under the project, including a client repo: commit messages and public text carry no tooling attribution and no assistant vocabulary, no real names of users or reporters, and no live health figures, ever. Fixtures use invented data. If an AI tool wrote part of a change, the human who commits it has read it and stands behind it; the git history knows only authors.
+The privacy rules apply to any repo under the project, including a client repo: commit messages and public text carry no real names of users or reporters and no live health figures, ever. Fixtures use invented data. Whoever commits a change has read it and stands behind it.
 
 Secrets never appear in code, fixtures, or examples, not even placeholder-shaped real ones. Anything user-identifying stays out of logs on the client just as it does on the server.