[FEATURE] "You should know" mod: respect the `language` setting instead of always writing in English

Preflight Checklist

• [x] I have searched existing requests and this feature hasn't been requested yet
• [x] This is a single feature request (not multiple features)

Problem Statement

The built-in "You should know" mod (cc-plugin-you-should-know@builtin) always writes its notes and explanations in English. My sessions are in Turkish, but the notes still arrive in English.

The cause appears to be the side agent's prompt. It asks for "plain English" in several places ("explain it in plain English", "Plain English:", "Anything you write should be in plain-English"). In context this most likely means simple, jargon-free wording: the same lines ask to explain technical terms and avoid complex sentences. The model, however, reads it as a language instruction. Claude Code's own language setting reaches the session, and the side agent works on a fork of it, but the later and more specific "plain English" instruction conflicts with that setting.

The mod is meant to explain something at a glance to someone busy with other work. A note in the reader's second language works against that.

Proposed Solution

• In the side agent's two prompts (the suggestion and the "explain" request), say "plain language" instead of "plain English". Write in the language from the language setting, and match the user's language when it is unset.
• Keep the machine-read parts fixed in every language: learn:, learn: none, tag:, explain: and the tag values You should know / Heads up. The parser matches these English words, so the prompt should say explicitly not to translate them.

Alternative Solutions

For now I work around it with a small mod. It hooks model.fork and, when the caller is cc-plugin-you-should-know, appends an instruction to write in Turkish while keeping the keywords in English:

on('model.fork', ($, e, next) =>
  next.origin.plugin === 'cc-plugin-you-should-know'
    ? next({ ...e, prompt: e.prompt + TURKISH_INSTRUCTION })
    : next(e),
)

It works but is fragile: it depends on the plugin's name and on the parser's English keywords, so any update can break it. Language support belongs in the mod itself.

Priority

Medium - Would be very helpful

Feature Category

Configuration and settings

Use Case Example

1. "language": "turkish" is set in ~/.claude/settings.json, and the session is in Turkish.
2. While Claude works on a long task, the side agent finds something the user should know. For example, a debug token that was just added opens access to the real project, not only the test environment.
3. The "Heads up" note and the "explain" reply arrive in Turkish, so the user gets the point at a glance.

Additional Context

• Claude Code 2.1.288, macOS.
• Same pattern as #32058 (Ctrl+E permission explanation) and #81565 (/rename): a side feature with a hardcoded English prompt that bypasses the language setting.
• Related but out of scope: the UI labels ("Heads up", "You should know", "Understood", "Chat in main session", "Dismiss") are also hardcoded in English. This request covers only the note and explanation text.
• I'm filing an issue rather than a PR because this mod's source isn't published in the repo's mods/ folder.