A general-purpose crate at experimental/fileset/ that filters files from a directory using a gitignore-like manifest: the `fileset` library (the Fileset parser/matcher plus a filter_tree walk-and-copy helper) and a thin CLI (`fileset --fileset <manifest> <src> <out>`). Packaged as its own crane flake with clippy/fmt/audit/nextest checks; the manifest format (globs, `!` negation, `@import`) is documented in the crate README. This generalizes the fileset pre-filter previously bundled inside owl; the next commit removes owl's copy and rewires owl to consume this flake. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_0112UhDj44J8KdzZdE4xQPKX