make 'transitions < logs/dump.bin' a reality

because of the potentially trailing log data we can't safely seek to
the last frame without using a logs parser. thus the teeing logic
needs to be moved into the fuzzer.

src/test/fuzz.ts

@@ -8,7 +8,7 @@ import {promisify} from 'util';
 import {Generations} from '@pkmn/data';
 import {Dex} from '@pkmn/sim';
 
-import {LAYOUT, LE} from '../pkg/data';
+import {LE} from '../pkg/data';
 import * as debug from '../tools/debug';
 
 const ROOT = path.resolve(__dirname, '..', '..');
@@ -51,9 +51,6 @@ export async function run(
       if (e.code !== 'EEXIST') throw e;
     }
 
-    const size = LAYOUT[+gen - 1].sizes.Battle + 3;
-    fs.writeFileSync(path.join(dir, 'dump.bin'), stdout.subarray(stdout.byteLength - size));
-
     seed = LE ? stdout.readBigUInt64LE(0) : stdout.readBigUInt64BE(0);
     const hex = `0x${seed.toString(16).toUpperCase()}`;
     const file = path.join(dir, `${hex}.fuzz.html`);

src/test/fuzz.zig

@@ -223,19 +223,34 @@ fn dump() !void {
         try w.writeInt(u16, 0, endian);
         try w.writeAll(initial);
 
-        if (frames) |frame| {
-            for (frame.items) |d| {
-                try w.writeAll(d.log);
-                try w.writeAll(d.state);
-                try w.writeStruct(d.result);
-                try w.writeStruct(d.c1);
-                try w.writeStruct(d.c2);
+        if (frames) |fs| {
+            for (fs.items) |f| {
+                try w.writeAll(f.log);
+                try w.writeAll(f.state);
+                try w.writeStruct(f.result);
+                try w.writeStruct(f.c1);
+                try w.writeStruct(f.c2);
             }
         }
         if (buf) |b| try w.writeAll(b.items);
     }
 
     try bw.flush();
+
+    if (frames) |fs| {
+        if (fs.items.len > 0) {
+            // Write the last state information to the logs/ directory if it exists
+            // so that it can be trivially reproduced via the transitions tool
+            const file = std.fs.cwd().createFile("logs/dump.bin", .{}) catch return;
+            defer file.close();
+            var fw = file.writer();
+            const f = fs.items[fs.items.len - 1];
+            try fw.writeAll(f.state);
+            try fw.writeStruct(f.result);
+            try fw.writeStruct(f.c1);
+            try fw.writeStruct(f.c2);
+        }
+    }
 }
 
 pub fn panic(