bug: asdf install is not transactional

[ajfabbri]

Describe the Bug

Simplistic reproduction below... Related: #2036

Steps to Reproduce

asdf install python 4

This fails, as python 4 doesn't exist.

 % asdf list python
  4
% asdf install python 4
error installing version: version {version 4} of python is already installed

Expected Behaviour

Installation should fail or succeed, not some partial combination of both.

Actual Behaviour

asdf list python

% asdf list python
4
% asdf install python 4
error installing version: version {version 4} of python is already installed

### Environment

```shell
OS:
Darwin redacted.local 24.6.0 Darwin Kernel Version 24.6.0: Mon Jul 14 11:30:40 PDT 2025; root:xnu-11417.140.69~1/RELEASE_ARM64_T6041 x86_64

SHELL:
zsh 5.9 (x86_64-apple-darwin24.0)

BASH VERSION:
3.2.57(1)-release

ASDF VERSION:
v0.16.0

ASDF INTERNAL VARIABLES:
ASDF_DEFAULT_TOOL_VERSIONS_FILENAME=.tool-versions
ASDF_DATA_DIR=/Users/foo/.asdf
ASDF_CONFIG_FILE=/Users/foo/.asdfrc

ASDF INSTALLED PLUGINS:
gradle    https://github.com/rfrancis/asdf-gradle.git 3af56332a66b90f2c0743f2968b9f0425c479b94
java      https://github.com/halcyon/asdf-java.git    96f89465a471de99ae9c413d922c25f436537105
nodejs    https://github.com/asdf-vm/asdf-nodejs.git  fd2c7f94c4c71416047cacf2af6e4fa819b364b7
python    https://github.com/danhper/asdf-python.git  d4caa7d4832313b4c141ee0ceca4118747147e89
ruby      https://github.com/asdf-vm/asdf-ruby.git    26be0ebf43b47dba9bf244995700deeaa572b281

asdf plugins affected (if relevant)

python