`DiffRenderable` — unified and split diffs

Renders a unified-diff text (as produced by git diff / diff -u) with per-line coloring, line numbers, and a choice of unified or split view. Use it to show file changes in the UI.

DiffRenderable::new(diff: Option<String>) -> Self

View modes

pub enum DiffViewMode { Unified, Split }
// set_view_mode(DiffViewMode)

Unified — one column; added lines on their own rows, removed lines on their own, context lines shared.
Split — two side-by-side panels: removed lines on the left, added on the right, aligned into paired change blocks.

Content

set_diff(String)   // replace the diff text

The widget parses standard unified diff syntax: ---/+++ file headers, @@ hunk headers (with -old,count +new,count positions), + adds, - removes, and context lines.

Colors

Setter	Default	Effect
`set_added_bg`	`#1a4d1a`	Background of added lines.
`set_removed_bg`	`#4d1a1a`	Background of removed lines.
`set_context_bg`	transparent	Background of context lines.
`set_added_sign_color`	`#22c55e`	Foreground of `+` added lines.
`set_removed_sign_color`	`#ef4444`	Foreground of `-` removed lines.
`set_hunk_header_fg`	`#828bb8`	`@@` header color.
`set_line_number_fg`	`#888888`	Line number color.
`set_added_line_number_bg` / `set_removed_line_number_bg`	transparent	Line-number column backgrounds.
`set_show_line_numbers(bool)`	`true`	Toggle the line-number gutter.

All color setters take RGBA directly (not ColorInput).

Rendering behavior

Added/removed lines get their background color and a +/- sign prefix.
Hunk and file headers are colored distinctly.
Line numbers are tracked from the @@ hunk headers (old line numbers for removals/context, new for additions/context).
In split view, panels are sized to fit the width, with a separator column, and line-number gutters sized to the largest number on each side.

Example

use cosh_tui::core::renderables::diff::{DiffRenderable, DiffViewMode};

let diff = "\
--- a/lib.rs
+++ b/lib.rs
@@ -1,3 +1,4 @@
 fn main() {
-    println!(\"old\");
+    println!(\"new\");
 }
";

let mut view = DiffRenderable::new(Some(diff.into()));
view.set_view_mode(DiffViewMode::Unified);
// view.render_self(&mut buf, area);

Next: text_table — bordered grid table.