Describe the bug

When linking to a project that uses non-numeric versions (latest, stable, etc) the titles of intersphinx links are formatted as:

(in project vfoo)

For example:

This looks strange and also can cause spelling checks to fail.

It would be great if the relevant code (here?) could only prepend "v" to the version if the version is numeric.

How to Reproduce

In conf.py:

extensions = [
    'sphinx.ext.intersphinx',
]

intersphinx_mapping = {
    'charmcraft': ('https://canonical-charmcraft.readthedocs-hosted.com/en/stable/', None),
}

Then in a .rst document:

:external+charmcraft:ref:`manage-charms`

Here's my testing repo: https://github.com/dwilding/intersphinx-test

Environment Information

Platform:              linux; (Linux-6.11.0-26-generic-x86_64-with-glibc2.39)
Python version:        3.12.3 (main, Jun 18 2025, 17:59:45) [GCC 13.3.0])
Python implementation: CPython
Sphinx version:        8.2.3
Docutils version:      0.21.2
Jinja2 version:        3.1.6
Pygments version:      2.19.2

Sphinx extensions

['sphinx.ext.intersphinx']

Additional context

No response