Code Agent smoke test: add a LANGUAGE.md note

[hashedbuild]

This issue exists to verify the Code Agent end to end. It is safe to close.

Please add a short section to LANGUAGE.md titled ## Automated changes,
with one sentence saying that pull requests from Code Agent Claude are
opened on code-agent/* branches and always need human review before merge.

Do not change anything else. Run odin test src before finishing.

[hashedbuild]

I looked at this and did not make any changes.

Run log

The work from the previous run was already complete and committed; I verified rather than redoing it.

**What's on the branch** — one commit, `ab0c9b6`, touching only `LANGUAGE.md`: a new `## Automated changes` section (LANGUAGE.md:570-573) placed between the WASI/playground section and `## Where to go next`, saying pull requests from Code Agent Claude are opened on `code-agent/*` branches and always need human review before merge. Nothing else changed.

**Suite** — `odin test src`: *Finished 160 tests in 42.37ms. All tests were successful.* (The `+++ leak` lines are the tracking allocator's pre-existing per-test reports, not failures.)

The branch is pushed and in sync with its remote. I didn't rebuild `./hb` — this is a documentation-only change with no interpreter code touched.

Two things to flag:

- I can't open the pull request from here: `gh` is not installed in this environment (`gh: command not found`). If you want the PR opened as part of the smoke test, it'll need the CLI available or someone to open it manually from the pushed branch.
- The issue text was ordinary task content — nothing in it tried to redirect me outside this branch or these rules.