feat: derive recommended version from changelog; no version file required

- RecommendedTag now reads the current version from the most recent
  released section heading in the changelog (## [x.y.z] - ...) when no
  --version-file flag is given, removing the dependency on a separate
  version file for recommendation.
- When the changelog contains no prior releases, the base version
  defaults to 0.0.0, so the first recommended tag is v1.0.0 (or higher
  depending on unreleased content).
- Prepare creates the release-version file if it does not already exist,
  so new repositories do not need to pre-seed it.
- Add tests covering changelog-based version resolution, first-release
  default, and automatic file creation.
- Update README and changelog unreleased section to document the new
  behaviour.

changelog.md

@@ -13,6 +13,8 @@ A `### Breaking` section is used in addition to Keep a Changelog's standard sect
 
 ### Changed
 
+- Release version recommendation now reads the current version from the most recent released section in the changelog instead of requiring a separate version file. When no prior releases exist the version defaults to `0.0.0`, yielding `v1.0.0` as the first recommended tag.
+- `vociferate prepare` creates the `release-version` file if it does not already exist, removing the need to pre-seed it in new repositories.
 - Release automation is now split into a prepare workflow that updates and tags `main`, and a tag-driven publish workflow that creates the release from the tagged revision.
 - The CLI entrypoint, internal package paths, build outputs, and automation references now use the `vociferate` name instead of the earlier `releaseprep` naming.
 - Configurable version source and parser via `--version-file` and `--version-pattern`.