fix(github-http): return None on malformed GHES port instead of raising

[jawwad-ali]

Description

resolve_github_release_asset_api_url is contracted to either resolve a browser release-download URL to its REST API asset URL or return None — every unresolvable case (unknown host, not-an-asset path, network error, missing asset) returns None. But the GHES branch builds the authority via parsed.port:

elif is_ghes:
    authority = hostname if parsed.port is None else f"{hostname}:{parsed.port}"

urllib's .port raises ValueError on a malformed port. So an allowlisted GHES host with a bad port (e.g. https://ghes.example:notaport/...) crashes the caller instead of returning None. Reproduced on main @ 92b7cf7: ValueError: Port could not be cast to integer value as 'notaport'.

Fix

Read parsed.port inside a try/except ValueError: return None, matching the function's existing graceful return None behavior.

Testing

New test_returns_none_on_malformed_ghes_port: an allowlisted GHES host with :notaport returns None and induces no network call. Fails before (ValueError — verified by source-stash), passes after. The existing valid-port GHES test still passes (happy path unchanged). Full test_github_http.py: 27 passed. uvx ruff check clean.

AI Disclosure

• I did use AI assistance (describe below)

Found and fixed with Claude Code (Claude Fable 5) under my direction. AI spotted the unguarded parsed.port against the function's return-None contract; I reproduced the ValueError, verified fail-before/pass-after, and reviewed the diff.