Writer: a START that fails for a reason of someone else's type still answers

ProcessStartMessage caught JFJochException only, the same narrow catch
ProcessPreflight had. Everything that makes a failed START reportable sits inside
that handler - the Error state, err, and the fatal ACK - so an exception of any
other type skipped all three and left the broker blocked on an ACK that never
came, with the detector about to be armed. It reads that silence as a dead writer
and reports a timeout instead of the reason, and the writer is left out of the
Error state it should have entered.

Not every thrower on this path is ours: std::filesystem::exists throws
filesystem_error when the output path cannot be walked at all (a directory
component with no search permission, a symlink loop), and
SetupFinalizedFileSocket throws ZeroMQ's own type. Now catches std::exception.
Logger::ErrorException already takes std::exception, so the handler body is
unchanged.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016L1qig74oYQzfUJJZbbxFh

writer/StreamWriter.cpp

@@ -78,7 +78,13 @@ void StreamWriter::ProcessStartMessage() {
                     image_puller_output.cbor->start_message->number_of_images);
         state = StreamWriterState::Started;
         NotifyTcpAck(TCPFrameType::START, true, false, TCPAckCode::None);
-    } catch (const JFJochException &e) {
+    } catch (const std::exception &e) {
+        // std::exception, not JFJochException: everything below this point - the error state, err,
+        // and above all the fatal ACK - is skipped if the exception escapes, and the broker is
+        // blocked on that ACK with the detector about to be armed. It would read the silence as a
+        // dead writer and report a timeout in place of the reason. Not every thrower here is ours:
+        // std::filesystem::exists throws filesystem_error when the output path cannot be walked,
+        // and SetupFinalizedFileSocket throws ZeroMQ's own type.
         logger.ErrorException(e);
         logger.Error("Error writing start message - switching to error state");
         state = StreamWriterState::Error;