Implement SSH Compression Phase 2: Integration

- Add compression_ctos/compression_stoc to EncryptionContext
- Default impl: CompressionContext::new(6)
- from_session_keys(): initialize compression fields
- enable_compression() method (based on KEX negotiation)
- server.rs: enable compression after NEWKEYS (if negotiated)

All 179 tests pass.

markbase-core/src/ssh_server/server.rs

@@ -321,6 +321,16 @@ fn perform_complete_kex_exchange(
         info!("Setting cipher mode to AES-CTR (MtE)");
         encryption_ctx.set_cipher_mode(CipherMode::AesCtr)?;
     }
+    
+    // Phase 2: 根据 KEX 协商结果启用压缩（compression_ctos / compression_stoc）
+    let compression_ctos = &kex_result.compression_ctos;
+    let compression_stoc = &kex_result.compression_stoc;
+    info!("KEX negotiated compression algorithms: ctos={}, stoc={}", compression_ctos, compression_stoc);
+    
+    if compression_ctos != "none" || compression_stoc != "none" {
+        info!("Enabling SSH compression");
+        encryption_ctx.enable_compression(compression_ctos, compression_stoc);
+    }
 
     Ok(encryption_ctx)
 }