refactor: use project-named state file and store prompt/params directly

- State filename now derives from config: cards.bulkgen.yaml produces
  .cards.bulkgen-state.yaml instead of .bulkgen.state.yaml
- Store resolved prompt text and extra params directly in state file
  instead of hashing them, making state files human-readable
- Only file input contents remain hashed (SHA-256)
- Thread project_name through builder and CLI
- Remove hash_string() and _extra_hash() helpers
- Update .gitignore pattern to .*.bulkgen-state.yaml

.gitignore

@@ -15,7 +15,7 @@ wheels/
 .pre-commit-config.yaml
 
 # bulkgen state
-.bulkgen.state.yaml
+.*.bulkgen-state.yaml
 
 # Nix
 result