The Cookbook → Dependencies tab reported llama-cpp-python[server] as "not
installed" even when it was installed and usable for serving. The local check
looked up distribution metadata as pkg["name"].replace("_", "-") — for the
import name `llama_cpp` that yields "llama-cpp", but the module ships in the
`llama-cpp-python` distribution. importlib.metadata.version("llama-cpp") then
raised PackageNotFoundError and the package was marked missing (the import
itself succeeds, which is why serving still worked).
Derive the distribution name from the package's declared pip spec instead
(stripping [extras] and version markers), falling back to the munged import
name only when no pip spec is declared. New _pip_dist_name() helper.
Adds tests/test_cookbook_package_detection.py covering the llama_cpp mapping,
extras/marker stripping, plain names, the no-pip-spec fallback, and that the
route wires the helper in (guarding against the exact regression).
