Improve terminal rendering performance (#33345)

Closes #18263

Improvements:

• **Batch text rendering** - Combine adjacent cells with identical
styling into single text runs to reduce draw calls
• **Throttle hyperlink searches** - Limit hyperlink detection to every
100ms or when mouse moves >5px to reduce CPU usage
• **Pre-allocate collections** - Use `Vec::with_capacity()` for cells,
runs, and regions to minimize reallocations
• **Optimize background regions** - Merge adjacent background rectangles
to reduce number of draw operations
• **Cache selection text** - Only compute terminal selection string when
selection exists

Release Notes:

- Improved terminal rendering performance.

---------

Co-authored-by: Conrad Irwin <conrad.irwin@gmail.com>

crates/repl/src/outputs/plain.rs

@@ -259,20 +259,17 @@ impl Render for TerminalOutput {
                 cell: ic.cell.clone(),
             });
         let minimum_contrast = TerminalSettings::get_global(cx).minimum_contrast;
-        let (cells, rects) = TerminalElement::layout_grid(
-            grid,
-            0,
-            &text_style,
-            text_system,
-            None,
-            minimum_contrast,
-            window,
-            cx,
-        );
+        let (rects, batched_text_runs) =
+            TerminalElement::layout_grid(grid, 0, &text_style, None, minimum_contrast, cx);
 
         // lines are 0-indexed, so we must add 1 to get the number of lines
         let text_line_height = text_style.line_height_in_pixels(window.rem_size());
-        let num_lines = cells.iter().map(|c| c.point.line).max().unwrap_or(0) + 1;
+        let num_lines = batched_text_runs
+            .iter()
+            .map(|b| b.start_point.line)
+            .max()
+            .unwrap_or(0)
+            + 1;
         let height = num_lines as f32 * text_line_height;
 
         let font_pixels = text_style.font_size.to_pixels(window.rem_size());
@@ -300,15 +297,14 @@ impl Render for TerminalOutput {
                     );
                 }
 
-                for cell in cells {
-                    cell.paint(
+                for batch in batched_text_runs {
+                    batch.paint(
                         bounds.origin,
                         &terminal::TerminalBounds {
                             cell_width,
                             line_height: text_line_height,
                             bounds,
                         },
-                        bounds,
                         window,
                         cx,
                     );

crates/repl/src/outputs/table.rs

@@ -106,7 +106,9 @@ impl TableView {
 
         for field in table.schema.fields.iter() {
             runs[0].len = field.name.len();
-            let mut width = text_system.layout_line(&field.name, font_size, &runs).width;
+            let mut width = text_system
+                .layout_line(&field.name, font_size, &runs, None)
+                .width;
 
             let Some(data) = table.data.as_ref() else {
                 widths.push(width);
@@ -118,7 +120,7 @@ impl TableView {
                 runs[0].len = content.len();
                 let cell_width = window
                     .text_system()
-                    .layout_line(&content, font_size, &runs)
+                    .layout_line(&content, font_size, &runs, None)
                     .width;
 
                 width = width.max(cell_width)