better failure handling in main

src/main.zig

@@ -6,6 +6,7 @@ const stt = @import("stt.zig");
 
 /// Global flag for signal handling
 var should_exit = std.atomic.Value(bool).init(false);
+var fatal_error = std.atomic.Value(bool).init(false);
 
 // SAFETY: we are setting this value at top of main before use
 /// We need a global here to reclaim process when getting SIGCHLD
@@ -265,6 +266,12 @@ const SpeechHandler = struct {
             else
                 log.err("{s}", .{message}),
         }
+
+        // Signal shutdown on fatal errors
+        if (!error_info.recoverable) {
+            fatal_error.store(true, .release);
+            should_exit.store(true, .release);
+        }
     }
 };
 
@@ -315,7 +322,7 @@ pub fn main() !void {
     if (std.posix.getenv("ALSA_CONFIG_PATH") == null) {
         std.fs.cwd().access("alsa.conf", .{}) catch {
             _ = std.fs.File.stderr().writeAll("Error: alsa.conf file not found. Please put alsa.conf in the current directory or set ALSA_CONFIG_PATH\n") catch {};
-            std.process.exit(1);
+            return error.ConfigNotFound;
         };
         const c = @cImport({
             @cInclude("stdlib.h");
@@ -414,12 +421,12 @@ pub fn main() !void {
         }
         _ = try stderr.writeAll("Please download the model. A fine model can be downloaded from:\n");
         _ = try stderr.writeAll("\thttps://alphacephei.com/vosk/models/vosk-model-small-en-us-0.15.zip\n");
-        std.process.exit(1);
+        return error.ModelNotFound;
     }
 
     std.fs.cwd().access(model_path.?, .{}) catch {
         std.log.err("Model path does not exist: {s}", .{model_path.?});
-        std.process.exit(1);
+        return error.ModelNotFound;
     };
 
     // Initialize STT session with resolved model path
@@ -438,7 +445,7 @@ pub fn main() !void {
         std.log.err("  - Audio device '{s}' is available", .{options.audio_device});
         std.log.err("  - Model directory exists at: {s}", .{options.model_path});
         std.log.err("  - You have permission to access the audio device", .{});
-        return;
+        return err;
     };
     defer session.deinit();
 
@@ -468,7 +475,7 @@ pub fn main() !void {
                 std.log.err("Unexpected error during startup.", .{});
             },
         }
-        return;
+        return err;
     };
     defer session.stop();
 
@@ -504,6 +511,8 @@ pub fn main() !void {
         std.log.err("✗ {d} fatal errors occurred during speech recognition.", .{handler.error_count});
 
     _ = stdout.writeAll("Session completed successfully.\n") catch {};
+
+    if (fatal_error.load(.acquire)) return error.FatalError;
 }
 
 test "handler callbacks" {