`Prefs::set` makes a JSON pointer of the key (`key.replace('.', "/")`), so
`scripting/allowScriptsWriteFiles` resolves as well as the dotted spelling, and
the page on its own (`{key: "scripting", value: {…}}`) replaces every setting on
it — `coerce` takes an object for an object, and the page deserializes with
`serde(default)`. A prefix check on `scripting.` let both through. The page is
now read from the key's first segment, split on either separator.
Found by CodeRabbit on the pull request; reproduced before fixing, with
`prefs.set {key: "scripting/allowScriptsWriteFiles", value: true}` answering
`{"scripting/allowScriptsWriteFiles": true}` under confinement.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>