fix: create temporary files in same dir as end destination

To ensure that config and state files are mutated atomically, updates
are done by creating a temporary file, writing the new content, and
doing an `os.rename` call to replace the old file with the temporary
file. However, until this commit, the temporary file was create in the
OS' default temp dir. In some environment (Codespaces), this
directory isn't on the same filesystem as the target file.

The solution is to create the temp file in the target directory. It
might end up leaving some artifacts if the process were to die before
cleaning it up, but that's better than failing on such a common case as
having more multiple filesystems.

internal/pkg/state/state.go

@@ -68,7 +68,8 @@ func WriteStateFile(path string, state *State) error {
 	if err != nil {
 		return fmt.Errorf("marshaling state file: %v", err)
 	}
-	newf, err := os.CreateTemp(os.TempDir(), "humanlog_statefile")
+
+	newf, err := os.CreateTemp(filepath.Dir(path), "humanlog_statefile")
 	if err != nil {
 		return fmt.Errorf("creating temporary file for statefile: %w", err)
 	}