[ISSUE]: next-version must include tag-prefix

Prerequisites

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GitVersion package

GitVersion.Portable

GitVersion version

6.8.2

Operating system

Windows

What are you seeing?

When configuring tag-prefix to something non-optional, next-version cannot be used without including that prefix.

In a monorepo I've got a tag-prefix per package, like "package-a/v" and "package-b/v". If I then set next-version to something normal like "1.4.5", I get an error saying "Failed to parse 1.4.5 into a Semantic Version".

If I change next-version to package-a/v1.4.5, I get the desired result.

What is expected?

Since next-version is not a tag, it's a version, I don't see any reason for it to require the tag-prefix, it should just be read as-is as a version without stripping any tag.

Steps to Reproduce

This can be reproduced with a minimal config in any repo with at least one commit, no tags needed:

tag-prefix: 'project-a/'
# fails
next-version: 1.2.3
# works
next-version: project-a/1.2.3

RepositoryFixture Test

No response

Output log or link to your CI build (if appropriate).

Start by locating the parsing path for next-version and the handling of tag-prefix in the GitVersion codebase. Reproduce the issue with the minimal configuration shown, then add or update coverage for both prefixed and unprefixed next-version values. Done means next-version: 1.2.3 is accepted when tag-prefix is non-optional, while tag parsing remains unchanged.