Function project_changed_since 

pub fn project_changed_since(
    project_root: &Path,
    last_indexed_at: SystemTime,
    indexed_paths: &[String],
    options: DiscoveryOptions,
) -> bool

Returns true if any discovered file is newer than last_indexed_at (a modify or add) or any previously indexed path no longer exists on disk (a delete or rename), and false only when the on-disk tree still matches the recorded index. A false result lets the caller skip the advisory lock and the full re-hash entirely.

Discovery mirrors the indexer (walker::discover_files with DEFAULT_EXCLUDES), so the .gobby/plans/**/*.md allowlist and every other exclusion stay in lockstep with what actually gets indexed — including the internal .gobby/plans/*.md edits the daemon trigger never forwards. Short-circuits on the first sign of change.