docs(agents): scope changelog.md to a file-only deliverable

The v1.3.0 release pipeline broke because Copilot, invoked by
.github/workflows/tags.yaml with --allow-all-tools, committed the
generated changelog onto HEAD of main on its own. The workflow's
next step — `git checkout -b ... origin/main` — then wiped the file,
and `git add` failed with a pathspec error.

The root cause is in this document. The checklist ends with "Save
the changelog", which an agent with broad tool access can reasonably
interpret as "also commit it, push it, and open a PR". There was no
explicit boundary.

Add a "Scope and boundaries" section at the top and an explicit
"then exit" at the end of Step 9:

- The single deliverable is docs/changelogs/v<version>.md.
- Forbidden by default: git commit / push / checkout (to switch
  branches) / branch / tag / reset / merge / rebase; PR creation;
  GitHub API writes (POST/PATCH/DELETE); modifying any file other
  than the changelog.
- Read-only analysis (git log/show/fetch/diff, gh pr view, gh api
  GET) remains expected.
- Auxiliary repo clones under _repos/ remain allowed for cross-repo
  analysis per Step 6.
- Scoped "unless the caller explicitly instructs otherwise" so
  interactive use with an IDE remains flexible.

With the rules in the doc, CI and interactive callers share the
same boundary; the workflow can invoke the doc with a one-line
prompt instead of re-stating the constraints every time.

Signed-off-by: Myasnikov Daniil <myasnikovdaniil2001@gmail.com>

docs/agents/changelog.md

@@ -6,6 +6,20 @@ This file contains detailed instructions for AI-powered IDE on how to generate c
 
 Follow these instructions when the user explicitly asks to generate a changelog.
 
+## Scope and boundaries
+
+**Your single deliverable is the file `docs/changelogs/v<version>.md`.** Write the complete, verified changelog to that path. That is the entire task. Exit as soon as the file is written and verified against the checklist in Step 9.
+
+Unless the caller explicitly instructs otherwise:
+
+- **Do not** run `git commit`, `git push`, `git checkout` (to switch branches), `git branch`, `git tag`, `git reset`, `git merge`, `git rebase`, or any other command that writes to refs, HEAD, or remotes.
+- **Do not** create pull requests, push branches, or issue GitHub API write calls (POST / PATCH / DELETE).
+- In the cozystack working tree, the **only** file you create or modify is `docs/changelogs/v<version>.md`. Cloning auxiliary repositories under `_repos/` for cross-repo analysis (see Step 6) is fine — that directory is outside the cozystack tree.
+
+The caller — a GitHub Actions workflow in CI, or a developer running you interactively — owns branching, committing, pushing, and PR creation. They will perform those actions after you exit. Do not pre-empt them even if the working tree looks ready.
+
+Read-only analysis is expected and encouraged: `git log`, `git show`, `git fetch`, `git diff`, `gh pr view`, `gh api` GET requests, and reading any file in the repository.
+
 ## Required Tools
 
 Before generating changelogs, ensure you have access to `gh` (GitHub CLI) tool, which is used to fetch commit and PR author information. The GitHub CLI is used to correctly identify PR authors from commits and pull requests.
@@ -608,6 +622,8 @@ Create a new changelog file in the format matching previous versions:
 **Save the changelog:**
 Save the changelog to file `docs/changelogs/v<version>.md` according to the version for which the changelog is being generated.
 
+**Then exit.** Do not commit, push, create a branch, or open a pull request — the caller handles all git and GitHub operations after you return. See the "Scope and boundaries" section at the top of this document.
+
 ### Important notes
 
 - **After fetch with --force** local tags are up-to-date, use them for work