instructions: the agent speaks the KB language in chat - AGENTS.md § Conversation language, and instructions sync compiles the language tag into every published SKILL.md (#116); 10.0.0-beta.9

Files changed:
- AGENTS.md
- CHANGES.md
- VERSION
- docs/explanation/language-boundaries.md
- docs/reference/commands/types-instructions-and-docs.md
- instructions/CONTRACT.md
- instructions/dev/stack-build/SKILL.md
- instructions/dev/stack-close/SKILL.md
- instructions/dev/stack-dev/SKILL.md
- kb/CONVENTIONS.md
- kb/CONVENTIONS.md.template
- tools/CONTRACT.md
- tools/chemenu/commands/doctor.py
- tools/chemenu/commands/instructions_cmd.py
- tools/chemenu/tests/test_doctor.py
- tools/chemenu/tests/test_instructions_cmd.py

Co-Authored-By: Claude Code <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01SnAJ7Z3CpVD3PRbN73QtU2

instructions/dev/stack-dev/SKILL.md

@@ -66,7 +66,7 @@ are split that way.
    - **A short one** - an existing spec refreshed against the tree: continue in this session
      with `/stack-build #N`.
 
-   Close with the fixed line, in the instance's KB language per `AGENTS.md` § File naming:
+   Close with the fixed line, in the instance's KB language per `AGENTS.md` § Conversation language:
 
    > #N is ready. Next: `/stack-build #N` - here, or after `/clear`.