patch: extract DMG layout AppleScript to tools/ (heredoc ≠ YAML)

The inline `osascript <<APPLESCRIPT` heredoc in the previous commit
broke YAML parsing — the end-marker has to live at column 0 for bash
to recognise it, but that falls below the block-scalar indent and
closes the `run:` block early. Workflow failed at load time in 0 s.

Move the AppleScript to `tools/dmg-layout.applescript` and invoke it
with the volume name as an argument. Same behaviour, no YAML grief.

Co-Authored-By: Claude Opus 4.7 (1M context) <[email protected]>

Author: Leitet

.github/workflows/release.yml

@@ -280,28 +280,9 @@ jobs:
           mkdir "$MOUNT/.background"
           cp Resources/dmg-background.png "$MOUNT/.background/background.png"
 
-          # 3. Finder layout — 640×400 window, icons at positions that
-          #    frame the background arrow.
-          osascript <<APPLESCRIPT
-          tell application "Finder"
-              tell disk "$VOL_NAME"
-                  open
-                  set current view of container window to icon view
-                  set toolbar visible of container window to false
-                  set statusbar visible of container window to false
-                  set the bounds of container window to {400, 150, 1040, 550}
-                  set viewOptions to the icon view options of container window
-                  set arrangement of viewOptions to not arranged
-                  set icon size of viewOptions to 128
-                  set background picture of viewOptions to file ".background:background.png"
-                  set position of item "Arc Transcriber.app" of container window to {128, 260}
-                  set position of item "Applications" of container window to {388, 260}
-                  update without registering applications
-                  delay 1
-                  close
-              end tell
-          end tell
-APPLESCRIPT
+          # 3. Finder layout — script lives in tools/ so the YAML
+          #    block doesn't have to deal with heredoc indentation.
+          osascript tools/dmg-layout.applescript "$VOL_NAME"
 
           # Flush and unmount
           sync

tools/dmg-layout.applescript

@@ -0,0 +1,37 @@
+-- Sourceful Arc Transcriber DMG installer-window layout.
+--
+-- Called from `.github/workflows/release.yml` during the "Package .dmg"
+-- step, with the volume name passed as an argument. Finder writes the
+-- layout it applies here into the volume's .DS_Store, so any user who
+-- mounts the published DMG sees the same window.
+--
+-- The arrow in the background image runs horizontally between the two
+-- icon slots; icon positions below are aligned to the arrow endpoints
+-- (app on the left at 128,260; Applications symlink on the right at
+-- 388,260 inside a 640×400 window).
+
+on run argv
+    set volName to item 1 of argv
+
+    tell application "Finder"
+        tell disk volName
+            open
+            set current view of container window to icon view
+            set toolbar visible of container window to false
+            set statusbar visible of container window to false
+            set the bounds of container window to {400, 150, 1040, 550}
+
+            set viewOptions to the icon view options of container window
+            set arrangement of viewOptions to not arranged
+            set icon size of viewOptions to 128
+            set background picture of viewOptions to file ".background:background.png"
+
+            set position of item "Arc Transcriber.app" of container window to {128, 260}
+            set position of item "Applications" of container window to {388, 260}
+
+            update without registering applications
+            delay 1
+            close
+        end tell
+    end tell
+end run