improve shortcut 'open with' handling

development.md

@@ -188,7 +188,15 @@ handlers in src/ipc/. Keep new APIs in that pattern.
   when it sits inside the prefix's drive_c, `Z:\...` otherwise. Giving a file
   to an app that is ALREADY running is a handoff (runGame `handoff: true`):
   an extra untracked process, no log/playtime writes, because the app's own
-  single-instance logic is what actually opens the file.
+  single-instance logic is what actually opens the file. The second-instance
+  handoff must never read a value from the token next to its option: Electron
+  RE-SERIALIZES that argv (all switches first, their values after, the dev app
+  path among them), so `--launch <id> --file <path>` arrives as
+  `--launch --file --allow-file-access-from-files <id> <path>`. argv.js pairs
+  options with positionals IN ORDER (inline `--name=value` wins, the dev app
+  path is skipped); reading the next token used to take the launch id as the
+  opened file, so an app started without its image.
+  `electron test/argv-handoff.test.js` proves the real serialization.
 - A sender hashing a big unit is minutes of network silence: it pings
   `/plwl/ping` (+token) every HEARTBEAT_MS for the whole sync, the receiver's
   handler re-arms its popup watchdog (stage 'wait' changes nothing on screen),