Python exception when running buildstream twice in the same command

When I run `bst show` to show a diff between two projects (e.g. to do `diff <(bst show ...) <(bst show ...)`) I sometimes get exceptions - the stack trace of one is below.

I was using `-C` to switch to a different buildstream project, if that makes any difference.

I installed recently in a venv, through pip:

```
$ pip show buildstream
Name: BuildStream
Version: 2.3.0
Summary: A framework for modelling build pipelines in YAML
Home-page: https://buildstream.build
Author: The Apache Software Foundation
Author-email: dev@buildstream.apache.org
License: Apache License Version 2.0
Location: /home/john/src/project/.venv/lib64/python3.12/site-packages
Requires: Click, grpcio, Jinja2, pluginbase, protobuf, psutil, pyroaring, ruamel.yaml, ruamel.yaml.clib, setuptools, ujson
Required-by:
```

Traceback (modified only to hide project name):

```
Traceback (most recent call last):
File "/home/john/src/project/.venv/bin/bst", line 8, in
sys.exit(cli())
^^^^^
File "/home/john/src/project/.venv/lib64/python3.12/site-packages/click/core.py", line 1157, in __call__
return self.main(*args, **kwargs)
^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/home/john/src/project/.venv/lib64/python3.12/site-packages/buildstream/_frontend/cli.py", line 272, in override_main
original_main(self, args=args, prog_name=prog_name, complete_var=None, standalone_mode=standalone_mode, **extra)
File "/home/john/src/project/.venv/lib64/python3.12/site-packages/click/core.py", line 1078, in main
rv = self.invoke(ctx)
^^^^^^^^^^^^^^^^
File "/home/john/src/project/.venv/lib64/python3.12/site-packages/click/core.py", line 1688, in invoke
return _process_result(sub_ctx.command.invoke(sub_ctx))
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/home/john/src/project/.venv/lib64/python3.12/site-packages/click/core.py", line 1434, in invoke
return ctx.invoke(self.callback, **ctx.params)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/home/john/src/project/.venv/lib64/python3.12/site-packages/click/core.py", line 783, in invoke
return __callback(*args, **kwargs)
^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/home/john/src/project/.venv/lib64/python3.12/site-packages/click/decorators.py", line 45, in new_func
return f(get_current_context().obj, *args, **kwargs)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/home/john/src/project/.venv/lib64/python3.12/site-packages/buildstream/_frontend/cli.py", line 631, in show
with app.initialized():
^^^^^^^^^^^^^^^^^
File "/usr/lib64/python3.12/contextlib.py", line 137, in __enter__
return next(self.gen)
^^^^^^^^^^^^^^
File "/home/john/src/project/.venv/lib64/python3.12/site-packages/buildstream/_frontend/app.py", line 250, in initialized
self.context.artifactcache.preflight()
^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/home/john/src/project/.venv/lib64/python3.12/site-packages/buildstream/_context.py", line 482, in artifactcache
self._artifactcache = ArtifactCache(self)
^^^^^^^^^^^^^^^^^^^
File "/home/john/src/project/.venv/lib64/python3.12/site-packages/buildstream/_artifactcache.py", line 36, in __init__
super().__init__(context)
File "/home/john/src/project/.venv/lib64/python3.12/site-packages/buildstream/_assetcache.py", line 306, in __init__
self.cas: CASCache = context.get_cascache()
^^^^^^^^^^^^^^^^^^^^^^
File "/home/john/src/project/.venv/lib64/python3.12/site-packages/buildstream/_context.py", line 709, in get_cascache
self._cascache = CASCache(self.cachedir, casd=self.get_casd(), remote_cache=bool(self.remote_cache_spec))
^^^^^^^^^^^^^^^
File "/home/john/src/project/.venv/lib64/python3.12/site-packages/buildstream/_context.py", line 696, in get_casd
self._casd = CASDProcessManager(
^^^^^^^^^^^^^^^^^^^
File "/home/john/src/project/.venv/lib64/python3.12/site-packages/buildstream/_cas/casdprocessmanager.py", line 109, in __init__
self._logfile = self._rotate_and_get_next_logfile()
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/home/john/src/project/.venv/lib64/python3.12/site-packages/buildstream/_cas/casdprocessmanager.py", line 277, in _rotate_and_get_next_logfile
os.remove(os.path.join(self._log_dir, logfile_to_delete))
FileNotFoundError: [Errno 2] No such file or directory: '/home/john/.cache/buildstream/logs/_casd/1727856548.523361.log'
```

Start in src/buildstream/_cas/casdprocessmanager.py, especially _rotate_and_get_next_logfile(), using the traceback as the entry point. Reproduce the failure by running bst show twice with -C as described, then verify that repeated commands no longer raise the reported FileNotFoundError while rotating CASD logs.

Written by the indexing model from the issue text.