feat: --color

[Copilot]

Fixes #11.
Closes khai-slop-labs#1.

Adds --color [auto|always|never] support, coloring tree output using the LS_COLORS environment variable.

New components

• ColorWhen enum (src/args/color.rs) — Auto (default, TTY-detect) / Always / Never
• LsColors (src/ls_colors.rs) — wraps the lscolors crate; parses LS_COLORS into per-indicator ANSI prefix strings for Directory, Normal, Executable, Symlink
• Color + Coloring (src/visualizer/coloring.rs) — Coloring holds a HashMap<PathBuf, Color> (full-path keys) and the LsColors prefixes; node_color(&Path, has_children) drives per-node color selection

Integration

• Visualizer gains coloring: Option<&'a Coloring>; rows() wraps names in ANSI prefix/reset when set
• build_coloring_map in sub.rs walks the DataTree, classifying leaves as Symlink > Directory > Executable (Unix) > Normal; directory coloring for internal nodes is resolved in the visualizer via has_children
• App::run() evaluates TTY state + ColorWhen to construct and thread Coloring through to the visualizer

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[github-actions]

Performance Regression Reports

commit: 5f4ca71

There are no regressions.

[Copilot]

Pull request overview

Copilot reviewed 25 out of 26 changed files in this pull request and generated 3 comments.

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[Copilot]

When pdu is run with multiple path arguments (e.g., pdu path1 path2), the code inserts a synthetic root node whose name is later changed from "" to "(total)" at line 147, before build_coloring_map is called at line 203. As a result, build_coloring_map constructs paths such as (total)/path1/file.txt and calls file_color on them. Since (total)/path1/file.txt does not exist on the filesystem, is_symlink(), is_dir(), and is_executable() all return false, and every file gets the default Color::Normal color — ignoring the actual file type. Symlinks and directories will be miscolored (shown as normal files) whenever --color is used with multiple path arguments. A fix would be to reconstruct each file's actual path from the child sub-trees before calling file_color, or to build the coloring map for each sub-tree individually using its original root path.

Suggested change

	let mut map = HashMap::new();
	let mut map = HashMap::new();
	// NOTE: When `pdu` is invoked with multiple path arguments, a synthetic
	// root node (renamed to "(total)") is created. Calling `build_coloring_map`
	// on that synthetic root can lead to non-existent filesystem paths like
	// "(total)/path1/file.txt" being passed to `file_color`, which in turn
	// causes all filesystem-type checks (is_dir, is_symlink, etc.) to fail and
	// results in incorrect coloring. The intended behavior is to build the
	// coloring map per real subtree (each original argument) so that only
	// actual filesystem paths are used for type detection.
	//
	// For now, we keep the single-root behavior here; special handling for
	// synthetic aggregate roots should be implemented inside `build_coloring_map`
	// (by skipping synthetic roots and traversing their children individually).