Potential issue: dot-segment removal drops the trailing slash (RFC 3986 section 5.2.4), so "http://e.org/a/.." != "http://e.org/"

[Sun-Wukhan]

Found while property-based testing URL normalization.

httpx._urlparse.normalize_path claims to implement RFC 3986 section 5.2.4, but a trailing "." or ".." segment loses its trailing slash:

normalize_path("/..")       == ""     # RFC: "/"
normalize_path("/a/..")     == ""     # RFC: "/"
normalize_path("/a/.")      == "/a"   # RFC: "/a/"
normalize_path("/a/b/..")  == "/a"   # RFC: "/a/"

User-visible consequence:

httpx.URL("http://e.org/a/..") == httpx.URL("http://e.org/")   # False, expected True

Browsers (WHATWG) agree with the RFC here. The existing tests pin mid-path cases ("/abc/def/../ghi/./jkl" -> "/abc/ghi/jkl") but nothing with a trailing dot segment. Note the docstring example itself would change under a strict reading: normalize_path("/path/./to/somewhere/..") is currently documented as "/path/to", where the RFC algorithm gives "/path/to/" — so I wanted to check whether the current behaviour is a deliberate simplification before sending a PR.

The fix is ready on a fork branch: https://github.com/Sun-Wukhan/httpx/tree/fix/url-normalize-path-rfc (the full tests/models suite passes with it). Raising it here first since PR creation on this repo is limited to collaborators; happy for a maintainer to open the PR from the branch.