-- lsd / walk / glob — filesystem enumeration builtins. All three return a
-- Result so missing-dir / permission-denied surface as Err and compose
-- with `!`-unwrap and the `?ok{…}{…}` pattern. Paths are returned relative
-- to the requested root, with `/` separators on every OS, sorted
-- lexicographically for deterministic output across machines.
--
-- This file uses the repo's own `examples/` directory as a stable fixture so
-- it runs without setup under the engine-harness (cwd = crate root).
-- `lsd dir` — non-recursive listing. Returns just the filenames, not the
-- full paths; the caller `cat`s them with the dir prefix when they need
-- absolute references. Empty dirs return `[]`, not Err.
ls-has-entries dir:t>R b t;es=lsd! dir;~>len es 0
-- `walk dir` — recursive DFS, paths relative to `dir`, includes both file
-- and directory entries (matches `find` shape). Sorted output makes diffs
-- stable across runs.
walk-has-entries dir:t>R b t;ps=walk! dir;~>len ps 5
-- `glob dir pat` — shell-style filter on a recursive walk. Pattern syntax:
-- * any run within a path segment (does not cross `/`)
-- ? a single char within a segment
-- [abc] / [a-z] a char class; leading `!` or `^` negates
-- ** any number of nested segments (recursive)
--
-- `**/*.ilo` matches every .ilo file in the tree, including ones in the
-- immediate dir (the `**` matches zero segments too).
glob-ilo-count dir:t>R b t;ps=glob! dir "**/*.ilo";~>len ps 0
-- Missing directory surfaces as Err. The agent can pattern-match the
-- Result or use `?ok` to branch instead of carrying a sentinel value.
ls-missing>R (L t) t;lsd "this-path-must-not-exist-xyzzy"
-- run: ls-has-entries "examples"
-- out: true
-- run: walk-has-entries "examples"
-- out: true
-- run: glob-ilo-count "examples"
-- out: true
-- err: ls-missing
-- out: ^No such file or directory (os error 2)