stack: Changelog-Eintrag geschichtet - Impact-Gruppierung, version regrade, Zusammenfassungspflicht (schliesst #95)

Files changed:
- CHANGES.md
- DEVELOPMENT.md
- VERSION
- instructions/dev/stack-dev/SKILL.md
- instructions/dev/version-parts.md
- tools/CONTRACT.md
- tools/README.md
- tools/chemenu/commands/run_budget.py
- tools/chemenu/commands/version_cmd.py
- tools/chemenu/tests/test_run_budget.py
- tools/chemenu/tests/test_version_cmd.py
- tools/chemenu/version.py

tools/README.md

@@ -91,11 +91,16 @@ bound at import time - `KB_DIR` and friends follow whatever `ROOT` currently is.
 5. Raise the version: `wikitool version bump --minor --title "..."` for a new
    command (`--patch` for a fix, `--major` when the new version is **not a
    drop-in replacement** - a renamed flag or artefact, a stricter check that
-   newly fails on content an instance already had, anything needing hand-work
-   after the copy). Content migration is one way to land there, not the
-   definition of it: a `--major` may well ship `--no-migration`, and one that
-   does migrate also needs a document under `instructions/migrations/`. The
-   full test is `instructions/dev/version-parts.md` - read it before choosing
+   newly fails on **shipped content an instance already had** (a `kb/` page,
+   an `instructions/*.md` file), anything needing hand-work after the copy).
+   A new command that is merely pickier about its *own* fresh input - a flag
+   it did not previously accept, a write it now refuses without more from the
+   caller - is the ordinary MINOR case: nothing an instance already has stops
+   validating, there is simply more to say when the command is next invoked.
+   Content migration is one way to land in the MAJOR row, not the definition
+   of it: a `--major` may well ship `--no-migration`, and one that does
+   migrate also needs a document under `instructions/migrations/`. The full
+   test is `instructions/dev/version-parts.md` - read it before choosing
    `--major`.
    A new command reaches every future instance, and CI's version gate refuses a
    stack change that moved no version.