handle write failed due to piping through commands like head

src/main.zig

@@ -161,6 +161,18 @@ fn resolveUserPath(
 }
 
 pub fn main() !u8 {
+    return runCli() catch |err| switch (err) {
+        // Downstream pipe closed (e.g., `zfin earnings AAPL | head`). Zig's
+        // file writer surfaces EPIPE as WriteFailed. Treat as a clean exit
+        // — the consumer got what it needed and closed the pipe; further
+        // output isn't an error from our perspective. Matches `ls | head`,
+        // `git log | head`, etc.
+        error.WriteFailed, error.BrokenPipe => 0,
+        else => err,
+    };
+}
+
+fn runCli() !u8 {
     // Long-lived allocator for things that span the whole process. Only
     // actually used for the early argsAlloc and the TUI path — CLI
     // commands run under a per-invocation arena (see below).