found the issue. There is a badly escaped " in .local/share/nvim-lazy/lazy/friendly-snippets/snippets/zig.json:
[...]
"const exe = b.addExecutable(.{",
".name = \"${1}",\",
".root_source_file = b.path(\"${2: path}\"),",
[...]
notice the second line… it should be
[...]
"const exe = b.addExecutable(.{",
".name = \"${1}\",",
".root_source_file = b.path(\"${2: path}\"),",
[...]
Made a PR.