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

tools/CONTRACT.md

@@ -2542,6 +2542,7 @@ Publish every `instructions/<name>/SKILL.md` into the harness skill directories.
 **NOTES**
 
 - Publishes every `instructions/<name>/SKILL.md` into `.agents/skills/` and `.claude/skills/` as **copies**, and deletes published skills whose source is gone.
+- Each published `SKILL.md` is its source plus one generated line directly under the frontmatter: the `language:` of `kb/CONVENTIONS.md` and a pointer to `AGENTS.md` § Conversation language, so the agent has the value in context when the task begins. The frontmatter and every other file are copied unchanged. With no language declared, the `SKILL.md` is copied unchanged too, and the success message says so.
 - Both targets are gitignored, so a fresh clone runs this once.
 - Re-running repairs a drifted copy: the source always wins.
 - `--force` is required only to replace a target directory that is not a published skill at all (no `SKILL.md` in it).
@@ -2577,7 +2578,7 @@ Check the instruction layer.
 - 0    success
 - 1    Nothing found under `instructions/` at all, or a malformed instruction or `SKILL.md`
 - 1    A `SKILL.md` carries a relative markdown link
-- 1    A published copy drifted from its source
+- 1    A published copy drifted from its source - including a language line that belongs to an earlier `language:` (the message names it as such)
 - 1    An instruction nothing references, or a `manual: true` one that IS linked from AGENTS.md, CLAUDE.md or a skill and so risks running implicitly
 - 1    Something under `instructions/dev/` is referenced from outside it and outside a `dist:strip` block
 
@@ -2585,7 +2586,7 @@ Check the instruction layer.
 
 - Nothing found under `instructions/` at all, or a malformed instruction or `SKILL.md` -> Fix the flagged file, then re-run
 - A `SKILL.md` carries a relative markdown link -> Rewrite it as a repo-root-relative plain path, then re-run
-- A published copy drifted from its source -> Re-run `instructions sync` - the source under `instructions/` always wins
+- A published copy drifted from its source - including a language line that belongs to an earlier `language:` (the message names it as such) -> Re-run `instructions sync` - the source under `instructions/` always wins
 - An instruction nothing references, or a `manual: true` one that IS linked from AGENTS.md, CLAUDE.md or a skill and so risks running implicitly -> Link it from where it is used, or drop the link to a manual one, then re-run
 - Something under `instructions/dev/` is referenced from outside it and outside a `dist:strip` block -> Remove the reference or wrap it in a `dist:strip` block, then re-run
 
@@ -2597,7 +2598,7 @@ Check the instruction layer.
 
 - Flat instructions validate against `types/instruction.schema.yaml`, and each `SKILL.md` carries the frontmatter its harness reads.
 - No `SKILL.md` carries a relative markdown link: `sync` copies it to a different depth than the source, so a `SKILL.md` references a target as a repo-root-relative plain path instead (`instructions/CONTRACT.md` § "A skill's outbound reference is a plain path, not a link").
-- Every published copy is byte-identical to its source. Missing *every* copy is reported as "run sync", not as drift - that is a clean checkout.
+- Every published copy is what `sync` would write from its source: byte-identical, except for the generated language line in `SKILL.md` that the current `language:` of `kb/CONVENTIONS.md` calls for. Missing *every* copy is reported as "run sync", not as drift - that is a clean checkout.
 - No instruction is left that nothing references; one marked `manual: true` must instead not be linked from AGENTS.md, CLAUDE.md or a skill.
 - Nothing under `instructions/dev/` is referenced from outside it; a `<!-- dist:strip-start/end -->` block is exempt (`instructions/CONTRACT.md`).
 - Read-only.