`uv init --package` generates an invalid layout for `-stubs` packages

### Summary `uv init --package` generates a regular package layout for distribution names ending in `-stubs`, but `uv_build` interprets those names as stub-only packages. For example: ```console $ uv init --package foo-stubs $ cd foo-stubs $ uv build Building source distribution (uv build backend)... × Failed to build `/private/var/folders/7s/tk9b38l11172qj8b4r1f17r80000gn/T/tmp.fsPhXVeHko/foo-stubs` ╰─▶ Expected a Python module at: src/foo-stubs/__init__.pyi ``` This is because initialization generates: ```text src/foo_stubs/__init__.py ``` However, `uv_build` recognizes the `-stubs` suffix and expects: ```text src/foo-stubs/__init__.pyi ``` `uv init` should either reject `-stubs` names for templates that generate regular runtime packages, or generate a compliant stub-only package layout while preserving the literal `-stubs` suffix. Found while reviewing #17841. ### Platform all ### Version 0.11.18 ### Python version _No response_