chore(claude): add private-name rule

Mirror of the rule landed in socket-lib + socket-repo-template. Omit
private repo and internal project names from public-surface text;
don't substitute a placeholder.

Author: jdalton

CLAUDE.md

@@ -138,6 +138,8 @@ See `docs/references/error-messages.md` for worked examples and anti-patterns.
 
 - **minimumReleaseAge**: NEVER add packages to `minimumReleaseAgeExclude` in CI. Locally, ASK before adding — the age threshold is a security control.
 
+- 🚨 **NEVER mention private repos or internal project names** in commits, PR titles/descriptions/comments, issues, release notes, or any public-surface text. Internal codenames, unreleased product names, internal tooling repo names not on the public org page, customer names, partner names — none belong in public surfaces. **Omit the reference entirely.** Don't substitute a placeholder ("an internal tool", "a downstream consumer", etc.) — the placeholder itself is a tell that something is being elided. Rewrite the sentence to not need the reference at all.
+
 ## 📚 SHARED STANDARDS
 
 - Commits: [Conventional Commits](https://www.conventionalcommits.org/en/v1.0.0/) `<type>(<scope>): <description>` — NO AI attribution