fix: update error output for clarity, update docs for tofuenv use

[anastasiiakozlova245]

Updated logging for tofuenv use and install commands, updated readme.

Before:

• run tofuenv use without arguments
• Output:
  No versions matching 'latest:^[0-9]\+\.[0-9]\+\.[0-9]\+$' found in remote

After:

• run tofuenv use without arguments
• Output:
  No latest versions matching '^[0-9]\+\.[0-9]\+\.[0-9]\+$' found in remote

This change improves clarity about the exact regex used to search and excludes confusion that might be caused by the previous error description.

Tests:
tofuenv use latest:2.10
No latest versions matching '2.10' found in remote
tofuenv use 2.1.0
No 2.1.0 versions matching '^2.1.0$' found in remote
tofuenv use latest:^0.8
No latest versions matching '^0.8' found in remote

[kvendingoldo]

lgtm