feat: пересылка клиентских заголовков в апстрим (кроме служебных); Authorization — только ключ провайдера

src/commonTest/kotlin/pw/binom/llmproxy/ConfigLogicTest.kt

@@ -4,6 +4,7 @@ import kotlin.test.Test
 import kotlin.test.assertEquals
 import kotlin.test.assertFalse
 import kotlin.test.assertTrue
+import io.ktor.http.headersOf
 import kotlinx.serialization.json.Json
 import kotlinx.serialization.json.JsonObject
 import kotlinx.serialization.json.jsonArray
@@ -275,6 +276,42 @@ class ConfigLogicTest {
         assertEquals(null, pickFreeUpstream(pool, active, emptySet())?.id)
     }
 
+    @Test
+    fun headersToForwardKeepsUnknownAndDropsServiceHeaders() {
+        val req = headersOf(
+            "X-Opencode-Session" to listOf("abc-123"),
+            "X-Custom" to listOf("a", "b"),
+            "Host" to listOf("proxy:8100"),
+            "Content-Length" to listOf("42"),
+            "Transfer-Encoding" to listOf("chunked"),
+            "Connection" to listOf("keep-alive"),
+            "TE" to listOf("trailers"),
+            "Proxy-Connection" to listOf("keep-alive"),
+            "Upgrade" to listOf("h2c"),
+            "Authorization" to listOf("Bearer client-secret"),
+            "Accept" to listOf("*/*"),
+        )
+        val out = headersToForward(req)
+        assertEquals(listOf("abc-123"), out["X-Opencode-Session"])
+        assertEquals(listOf("a", "b"), out["X-Custom"])
+        assertEquals(listOf("*/*"), out["Accept"])
+        assertEquals(3, out.size)
+        assertEquals(null, out["Authorization"])
+    }
+
+    @Test
+    fun headersToForwardIsCaseInsensitiveOnSkipSet() {
+        val out = headersToForward(
+            headersOf(
+                "HOST" to listOf("x"),
+                "Content-length" to listOf("1"),
+                "x-opencode-session" to listOf("s"),
+            ),
+        )
+        assertEquals(1, out.size)
+        assertEquals(listOf("s"), out["x-opencode-session"])
+    }
+
     @Test
     fun rebuildFromChunksPreservesAllUpstreamFields() {
         val sse = """