apply button fails

I tried to use the Apply button, with v0.127.0 of the extension installed and v3.158.1 of appmap.

After a couple of tries, I persuaded Navie that the path to the file I wanted to update waslib/tasks/fixture.rake. When I hit the button, I got a red X, and the error

98124 [Stderr] [file-update] Failed to write file lib/tasks/fixture.rake: ENOENT: no such file or directory, mkdir 'lib'

in the log.
The working directory for both the RPC service and the Code Helper that spawned it is /:

ajp@Alans-MacBook-Pro appmap-python % pstree -p 98124
-+= 00001 root /sbin/launchd
 \-+= 15240 ajp /Applications/Visual Studio Code.app/Contents/MacOS/Electron
   \-+- 97715 ajp /Applications/Visual Studio Code.app/Contents/Frameworks/Code Helper (Plugin).app/Contents/MacOS/Code Helper (Plugin) --type=utility
     \--- 98124 ajp /Users/ajp/.appmap/bin/appmap rpc --port 0

ajp@Alans-MacBook-Pro appmap-python % lsof -Pn -p 98124 | head
COMMAND     PID USER   FD      TYPE             DEVICE  SIZE/OFF      NODE NAME
appmap-v3 98124  ajp  cwd       DIR                1,9       640         2 /
appmap-v3 98124  ajp  txt       REG                1,9 170662960 348291763 /Users/ajp/.appmap/lib/appmap/appmap-v3.158.1

ajp@Alans-MacBook-Pro appmap-python % lsof -Pn -p 97715 | head
COMMAND     PID USER   FD      TYPE             DEVICE  SIZE/OFF                NODE NAME
Code\x20H 97715  ajp  cwd       DIR                1,9       640                   2 /
Code\x20H 97715  ajp  txt       REG                1,9    116672           348166546 /Applications/Visual Studio Code.app/Contents/Frameworks/Code Helper (Plugin).app/Contents/MacOS/Code Helper (Plugin)

which seems like a case that's going to be common.
When I asked Navie to use the absolute path to the file, the Apply button worked just as I hoped it would.

Start by tracing the Apply button's file-update path through the RPC service and Code Helper, using the reported relative path lib/tasks/fixture.rake and working directory /. Reproduce the failure with a relative path, then verify that Apply writes the project file successfully when the process starts in /.