Restore transcriber output silencing without shell interpolation

The argv form dropped the old &>/dev/null redirect, so the transcriber
output leaked to mpv terminal. Keep the command string a constant and
pass the paths as positional parameters: no interpolated shell input
(so a filename can not be parsed as shell syntax) while the redirect
that silenced the output is restored.

Verified end-to-end through the script, with the real binding and a
media file named evil$(touch PWNED).wav: argv arrived intact as a
single argument, LD_LIBRARY_PATH preserved, payload inert, no leak.

scripts/export-loop-webp.lua

@@ -309,7 +309,7 @@ local function export_both()
     end
 
     for i, j in ipairs(jobs) do
-        mp.command_native({
+        mp.command_native_async({
             name = "subprocess", args = j.args,
             playback_only = false, capture_stdout = false, capture_stderr = false,
         }, function(success, result, err)

scripts/export-loop.lua

@@ -238,7 +238,7 @@ local function export_loop()
         -- Only normal (no adjustments — skip making an identical duplicate)
         osd_msg(string.format("Exporting loop (normal) ..."), 2)
 
-        mp.command_native({
+        mp.command_native_async({
             name = "subprocess", args = normal_args,
             playback_only = false, capture_stdout = false, capture_stderr = false,
         }, function(success, result, err)
@@ -289,7 +289,7 @@ local function export_loop()
     for i = 1, 2 do
         local idx = i
         local args = (idx == 1) and normal_args or modified_args
-        mp.command_native({
+        mp.command_native_async({
             name = "subprocess", args = args,
             playback_only = false, capture_stdout = false, capture_stderr = false,
         }, function(success, result, err)

scripts/screenshot-duo.lua

@@ -142,7 +142,7 @@ local function capture_pair()
     print(string.format("[screenshot-duo] Normal:   %s", normal_path))
     print(string.format("[screenshot-duo] Modified: %s", modified_path))
 
-    mp.command_native({
+    mp.command_native_async({
         name = "subprocess",
         args = ffmpeg_args,
         playback_only = false,

scripts/transcribe-subtitles.lua

@@ -60,13 +60,19 @@ local function transcribe()
     local transcriber = os.getenv("HOME") .. "/.local/bin/transcribe-video"
     mp.osd_message("Transcribing subtitles ...", 1)
 
-    local shell_cmd = "export LD_LIBRARY_PATH=/opt/cuda/targets/x86_64-linux/lib; "
-        .. transcriber .. " --srt \"" .. abs_path .. "\" \"" .. srt_path .. "\" &>/dev/null &"
-
+    -- Silence the transcriber's output like the old `&>/dev/null` did, but WITHOUT handing a
+    -- shell an interpolated path: the command string below is a constant, and the paths travel
+    -- as positional parameters ($1, $2), so a filename can never be parsed as shell syntax.
     mp.command_native({
         name = "subprocess",
-        args = { "bash", "-c", shell_cmd },
+        args = {
+            "sh", "-c",
+            "exec \"$0\" --srt \"$1\" \"$2\" >/dev/null 2>&1",
+            transcriber, abs_path, srt_path,
+        },
+        env = { "LD_LIBRARY_PATH=/opt/cuda/targets/x86_64-linux/lib" },
         playback_only = false,
+        detach = true,
     })
 
     poll_srt(srt_path, 0, 900)