fix: validate URL scheme in build_github_request (#2449)

* fix: validate URL scheme in build_github_request

* Potential fix for pull request finding

Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

* test: add missing hostname validation test for build_github_request

* fix: update docstring and fix import grouping per Copilot feedback

* fix: sort imports and simplify url validation in build_github_request

---------

Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

tests/test_github_http.py

@@ -0,0 +1,79 @@
+"""Tests for GitHub-authenticated HTTP request helpers."""
+
+import os
+from unittest.mock import patch
+
+import pytest
+
+from specify_cli._github_http import (
+    build_github_request,
+)
+
+
+class TestBuildGitHubRequest:
+    """Tests for build_github_request() URL validation and auth handling."""
+
+    # --- URL Validation Tests ---
+
+    def test_empty_url_raises_value_error(self):
+        """build_github_request() must reject an empty string URL."""
+        with pytest.raises(ValueError, match="url must not be empty"):
+            build_github_request("")
+
+    def test_whitespace_url_raises_value_error(self):
+        """build_github_request() must reject a whitespace-only URL."""
+        with pytest.raises(ValueError, match="url must not be empty"):
+            build_github_request("   ")
+
+    def test_non_http_url_raises_value_error(self):
+        """build_github_request() must reject URLs without http/https scheme."""
+        with pytest.raises(ValueError, match="url must start with http"):
+            build_github_request("not-a-url")
+
+    def test_ftp_url_raises_value_error(self):
+        """build_github_request() must reject ftp:// URLs."""
+        with pytest.raises(ValueError, match="url must start with http"):
+            build_github_request("ftp://github.com/file.zip")
+
+    # --- Valid URL Tests ---
+
+    def test_valid_https_url_returns_request(self):
+        """build_github_request() must return a Request for a valid https URL."""
+        req = build_github_request("https://github.com/github/spec-kit")
+        assert req.full_url == "https://github.com/github/spec-kit"
+
+    def test_valid_http_url_returns_request(self):
+        """build_github_request() must accept http:// URLs."""
+        req = build_github_request("http://example.com/file")
+        assert req.full_url == "http://example.com/file"
+
+    # --- Auth Header Tests ---
+
+    def test_github_token_added_for_github_host(self):
+        """Authorization header is set when GITHUB_TOKEN is present."""
+        with patch.dict(os.environ, {"GITHUB_TOKEN": "test-token", "GH_TOKEN": ""}):
+            req = build_github_request("https://github.com/github/spec-kit")
+        assert req.get_header("Authorization") == "Bearer test-token"
+
+    def test_gh_token_used_as_fallback(self):
+        """GH_TOKEN is used when GITHUB_TOKEN is absent."""
+        with patch.dict(os.environ, {"GITHUB_TOKEN": "", "GH_TOKEN": "fallback-token"}):
+            req = build_github_request("https://github.com/github/spec-kit")
+        assert req.get_header("Authorization") == "Bearer fallback-token"
+
+    def test_no_auth_header_for_non_github_host(self):
+        """Authorization header must NOT be set for non-GitHub URLs."""
+        with patch.dict(os.environ, {"GITHUB_TOKEN": "test-token"}):
+            req = build_github_request("https://example.com/file")
+        assert req.get_header("Authorization") is None
+
+    def test_no_auth_header_when_no_token(self):
+        """No Authorization header when no token is set in environment."""
+        with patch.dict(os.environ, {}, clear=True):
+            req = build_github_request("https://github.com/github/spec-kit")
+        assert req.get_header("Authorization") is None
+
+    def test_missing_hostname_raises_value_error(self):
+        """build_github_request() must reject URLs with valid scheme but no hostname."""
+        with pytest.raises(ValueError, match="url must include a hostname"):
+            build_github_request("http://")