docs: docs toc im Fehlerkontrakt, docs-verify-Zeile nennt die TOC-Pruefung, --major-Kriterium in tools/README.md korrigiert

Files changed:
- CHANGES.md
- VERSION
- tools/CONTRACT.md
- tools/README.md

tools/README.md

@@ -89,8 +89,14 @@ bound at import time - `KB_DIR` and friends follow whatever `ROOT` currently is.
    does not need a CLI runner - and a Typer callback called directly from a test
    receives `OptionInfo` objects, not values, for any argument the test omits.
 5. Raise the version: `wikitool version bump --minor --title "..."` for a new
-   command (`--patch` for a fix, `--major` when existing content has to be
-   migrated, which then also needs a document under `instructions/migrations/`).
+   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
+   `--major`.
    A new command reaches every future instance, and CI's version gate refuses a
    stack change that moved no version.