chore: remove unused import, clarify .gitignore comment

Drop the unused GitChanges import in api.py. Expand the .gitignore
comment on .contextzip/ to note it's project-local and that the
Gemini API key is never stored there.

.gitignore

@@ -36,6 +36,12 @@ desktop.ini
 # contextzip output files (don't commit test zips)
 *_context_*.zip
 
-# contextzip workspace
+# contextzip workspace — inbox/output/backups live here, project-local,
+# never meant to be committed (may contain manifests, backups of source
+# files, and applied zips). Note: the Gemini API key is NOT here — it's
+# stored outside the repo entirely, in the OS user-config dir
+# (~/.config/contextzip/config.json on Linux/macOS), so it was never at
+# risk from this file being missing.
+.contextzip/
 exports/
 

contextzip/api.py

@@ -47,7 +47,7 @@ from contextzip.filters import (
     resolve_files,
     resolve_files_from_git,
 )
-from contextzip.git import GitChanges, GitError, GitErrorKind, get_changed_files
+from contextzip.git import GitError, GitErrorKind, get_changed_files
 from contextzip.packager import PackageResult, create_zip_silent