fix: handle stream disconnection properly in curl transport and proxy handler (#108)

1. curl-cli-transport: signal error (not close) when curl exits with
non-zero code mid-stream, so downstream readers get a proper error
instead of a silent truncation.

2. proxy-handler: catch s.write() failures during streaming to detect
client disconnects, abort the upstream curl process, and stop the
stream cleanly instead of leaking resources.

3. proxy-handler: don't re-throw after sending error SSE event — the
stream is already closing, re-throwing causes unhandled rejection.

Co-authored-by: icebear0828 <icebear0828@users.noreply.github.com>

src/routes/shared/proxy-handler.ts

@@ -153,7 +153,13 @@ export async function handleProxyRequest(
               () => {},
               req.tupleSchema,
             )) {
-              await s.write(chunk);
+              try {
+                await s.write(chunk);
+              } catch {
+                // Client disconnected mid-stream — stop reading upstream
+                abortController.abort();
+                return;
+              }
             }
           } catch (err) {
             // P2-8: Send error SSE event to client before closing
@@ -161,7 +167,6 @@ export async function handleProxyRequest(
               const errMsg = err instanceof Error ? err.message : "Stream interrupted";
               await s.write(`data: ${JSON.stringify({ error: { message: errMsg, type: "stream_error" } })}\n\n`);
             } catch { /* client already gone */ }
-            throw err;
           } finally {
             // P0-2: Kill curl subprocess if still running
             abortController.abort();

src/tls/curl-cli-transport.ts

@@ -151,8 +151,14 @@ export class CurlCliTransport implements TlsTransport {
         }
         if (!headersParsed) {
           reject(new Error(`curl exited with code ${code}: ${stderrBuf}`));
+        } else if (code !== 0 && code !== null) {
+          // curl died mid-stream (e.g. connection reset, SIGPIPE) — signal error to reader
+          try {
+            bodyController?.error(new Error(`curl exited with code ${code} mid-stream: ${stderrBuf.trim() || "connection lost"}`));
+          } catch { /* stream already closed */ }
+        } else {
+          bodyController?.close();
         }
-        bodyController?.close();
       });
 
       child.on("error", (err) => {