Fix Windows context menu options not persisting across restarts

[asiloisad]

When I have enable the "Show in file/folder context menus" in Settings the entries appear correctly in File Explorer's context menu but do not work at all, and checkboxes revert to unchecked after Pulsar restart.

acc. Claude:
The root cause is in how winreg v1.2.1 spawns reg.exe internally: it uses child_process.spawn with shell: true, which routes the command through cmd.exe. The registry command values written by Pulsar contain both a quoted executable path and a %1 file argument placeholder. When passed through cmd.exe, the multiple quoted groups break argument boundary parsing, and %1 is expanded as a batch parameter (to an empty string). This causes reg.exe to exit with an "Invalid syntax" error, leaving the command subkey created but with an empty default value. The empty command means clicking the context menu entry does nothing. On the next restart, isRegistered() performs a strict string comparison between the stored value and the expected command string, which fails because the stored value is empty, so all checkboxes appear unchecked even though the keys exist in the registry. The fix replaces the winreg-based register() method with direct child_process.execFile calls using shell: false. This passes arguments to reg.exe as a proper array without any cmd.exe processing, so %1 is preserved literally and quoted paths are handled correctly. Reading and deregistration continue to use winreg unchanged, as those code paths are not affected by the issue.

I have tested it in local build and works fine.