fix(cli): Fix crash in templateflow get when matching one file

[effigies]

Currently:

❯ uvx templateflow get MNI152NLin6Asym --res 2 --desc LR -s T1w
Traceback (most recent call last):
  File "/home/chris/.cache/uv/archive-v0/N20Na8Y61YObB3kT5W_Jk/bin/templateflow", line 10, in <module>
    sys.exit(main())
             ~~~~^^
  File "/home/chris/.cache/uv/archive-v0/N20Na8Y61YObB3kT5W_Jk/lib/python3.13/site-packages/click/core.py", line 1157, in __call__
    return self.main(*args, **kwargs)
           ~~~~~~~~~^^^^^^^^^^^^^^^^^
  File "/home/chris/.cache/uv/archive-v0/N20Na8Y61YObB3kT5W_Jk/lib/python3.13/site-packages/click/core.py", line 1078, in main
    rv = self.invoke(ctx)
  File "/home/chris/.cache/uv/archive-v0/N20Na8Y61YObB3kT5W_Jk/lib/python3.13/site-packages/click/core.py", line 1688, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
                           ~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^
  File "/home/chris/.cache/uv/archive-v0/N20Na8Y61YObB3kT5W_Jk/lib/python3.13/site-packages/click/core.py", line 1434, in invoke
    return ctx.invoke(self.callback, **ctx.params)
           ~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/chris/.cache/uv/archive-v0/N20Na8Y61YObB3kT5W_Jk/lib/python3.13/site-packages/click/core.py", line 783, in invoke
    return __callback(*args, **kwargs)
  File "/home/chris/.cache/uv/archive-v0/N20Na8Y61YObB3kT5W_Jk/lib/python3.13/site-packages/templateflow/cli.py", line 144, in get
    click.echo('\n'.join(f'{match}' for match in api.get(template, **entities)))
                                                 ~~~~~~~^^^^^^^^^^^^^^^^^^^^^^
TypeError: 'PosixPath' object is not iterable

[effigies]

Rebased onto #143 to fix tests.

[effigies]

Given that the only failing test was unrelated and this was here for 8 months without objection, merging by lazy consensus after CI finishes unless someone wants to have a quick look.

[mgxd]

A few suggestions, looks good as is

[mgxd]

perhaps past the reach of this PR - but it would be nice to print out a more helpful message with empty lists, i.e.

Suggested change

	click.echo('\n'.join(filenames))
	if not filenames:
	click.echo('No files found.')
	return
	click.echo('\n'.join(filenames))

[effigies]

One currently useful feature is that the output is filenames. Helpful messages on stderr are fine, but I wouldn't want to change the utility of stdout to bash scripts.

Fine for another PR, but I don't want to scope creep this one.