I recommend symlinking (or copying every time) the crash file into the source directory and doing something akin to the following while testing:
test "fuzz test" {
try std.testing.fuzz(fuzzCtx, fuzzFn, .{
.corpus = &.{ @embedFile("crash") },
});
}
I also usually take advantage of @import("builtin").fuzz to print a human-readable input when rerunning in debug mode. Note that you will see two runs, one with your actual case and one with an empty input.
To answer your first question, the fuzzer does not continue running once it finds a crash, though the build system continues running for the webui.