perf(proxy): optimize hot request paths

- Cache route handlers, simplify NoRoute path normalization, and reduce matcher/header allocations

- Honor configured transport pool limits in auto mode and add hotpath regression benchmarks/tests

proxy/matcher_test.go

@@ -99,12 +99,24 @@ func TestMatcher_Compatibility(t *testing.T) {
 			config:       cfgWithAuth,
 			expectedUser: "owner", expectedRepo: "repo", expectedMatcher: "raw",
 		},
+		{
+			name:        "Malformed Raw Path (missing branch)",
+			rawPath:     "https://raw.githubusercontent.com/owner/repo",
+			config:      cfgWithAuth,
+			expectError: true, expectedErrCode: 400,
+		},
 		{
 			name:         "Gist Path",
 			rawPath:      "https://gist.github.com/user/abcdef1234567890",
 			config:       cfgWithAuth,
 			expectedUser: "user", expectedRepo: "", expectedMatcher: "gist",
 		},
+		{
+			name:         "Gist Path (user only)",
+			rawPath:      "https://gist.github.com/user",
+			config:       cfgWithAuth,
+			expectedUser: "user", expectedRepo: "", expectedMatcher: "gist",
+		},
 		{
 			name:         "Gist UserContent Path",
 			rawPath:      "https://gist.githubusercontent.com/user/abcdef1234567890",
@@ -135,6 +147,18 @@ func TestMatcher_Compatibility(t *testing.T) {
 			config:       cfgApiForceAllowed, // Auth disabled, but force allowed
 			expectedUser: "owner", expectedRepo: "repo", expectedMatcher: "api",
 		},
+		{
+			name:         "API Repos Path (missing repo)",
+			rawPath:      "https://api.github.com/repos/owner",
+			config:       cfgWithAuth,
+			expectedUser: "", expectedRepo: "", expectedMatcher: "api",
+		},
+		{
+			name:         "API Users Path (exact user)",
+			rawPath:      "https://api.github.com/users/someuser",
+			config:       cfgWithAuth,
+			expectedUser: "someuser", expectedRepo: "", expectedMatcher: "api",
+		},
 		{
 			name:        "Malformed GH Path (no repo)",
 			rawPath:     "https://github.com/owner/",