fix(pixelflux): Build the keyframe fuzz target, and lint every fuzz target on each push
codec.rs reads ledger::REFRESH_FINER since the capped constant quality's
refresh, and the keyframe target compiles codec.rs without the crate's
ledger module, so the daily fuzz build failed. The target stands the
constant in, as it does the reference module.
Each fuzz directory is a workspace of its own, so the workspace's clippy
never compiled the targets and only the fuzz workflow, on a pull request
or its daily run, would see one break. The clippy-fuzz hook checks all of
them with the fuzzing cfg cargo fuzz builds with, at each commit and in
the server lint job.