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and drop the dead link, and a reference to the unpublished planning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.

src/components/README.md

@@ -21,4 +21,4 @@ React components. The UI primitives are shadcn/ui (new-york style, zinc base) ov
 
 ## Conventions
 
-Kebab-case filenames; React component exports stay PascalCase regardless. (A handful of PascalCase-filename outliers under `medications/` + `onboarding/` are pre-existing drift, noted in [`../../CLAUDE.md`](../../CLAUDE.md).) Every `t()` call needs a matching key in `messages/en.json` — guarded by `i18n-call-site-coverage.test.ts`. Data reads go through TanStack Query with keys from `@/lib/query-keys` and unwrap `(await res.json()).data`. Tests live in [`__tests__/`](__tests__/).
+Kebab-case filenames; React component exports stay PascalCase regardless. Every `t()` call needs a matching key in `messages/en.json` — guarded by `i18n-call-site-coverage.test.ts`. Data reads go through TanStack Query with keys from `@/lib/query-keys` and unwrap `(await res.json()).data`. Tests live in [`__tests__/`](__tests__/).