project-create platform syntax

sentry project create accepts one or more [<org>/]<name>:<platform> arguments. The platform must be attached with :; never use a space-separated platform or --platform. Parse the final colon so names may contain colons, reject whitespace in names, and require every batch item to specify a platform. All explicitly prefixed projects must use the same organization; resolve that shared organization once. Keep command metadata, help, examples, generated documentation, skills, parsing, validation errors, and regression tests aligned with this syntax. Preserve object output for one successful project and use an array for multi-project or partial-batch results.