input: collection-owned tracked range decorations

Range decorations become an independently owned collection instead of a
global annotation list, and gutter markers and inline widgets are split out
of this change.

- Add `RangeDecorationCollection` with `set` / `append` / `clear` / `dispose`
  / `get_ranges`. Each collection owns only its own entries, so separate
  extensions cannot overwrite one another, and dropping a handle does not
  clear it. Public decoration IDs are gone; the handle owns lifetime.
- Share UTF-8 normalization and edit tracking between text and geometric
  decorations through a `TrackedDecoration` abstraction.
- Clip and project ranges through the shaped lines, so soft wraps,
  continuation indents, CRLF and folds no longer make a partly visible range
  disappear.
- Add an interval index queried once per visible, non-folded buffer span;
  edits update affected entries linearly without re-sorting.
- Remove gutter markers, gutter lane reservation, inline widgets, the
  `InputEvent::GutterMarkerMouseDown` variant and the `Editor` gutter
  renderer projection, plus their story/shell exhaustive-match arms.
- Update the English and Chinese docs and the Editor story.

Co-Authored-By: Claude <noreply@anthropic.com>

Author: feigeCode

crates/base/src/input/base/element.rs

@@ -29,7 +29,8 @@ use ropey::Rope;
 use super::decorations::DecorationCollections;
 use super::lsp::{ContextMenuContent, HoverDefinition, InlineCompletion};
 use crate::input::{
-    HighlightStyleResolver, InputEdit, InputHighlighter, SyntaxContext, TextDecoration,
+    HighlightStyleResolver, InputEdit, InputHighlighter, RangeDecoration, SyntaxContext,
+    TextDecoration,
 };
 use crate::input::{HoverPopoverState, Lsp};
 use gpui::Task;
@@ -82,6 +83,11 @@ pub trait InputExtras: Default + 'static {
         Vec::new()
     }
 
+    /// Geometric decorations intersecting visible, non-folded buffer spans.
+    fn range_decorations(&self, _ranges: &[std::ops::Range<usize>]) -> Vec<&RangeDecoration> {
+        Vec::new()
+    }
+
     /// Semantic-token styles for a visible range, when an LSP supplies them.
     fn semantic_token_styles(
         &self,
@@ -336,6 +342,7 @@ impl InputModeKind for TextareaMode {
 pub struct EditorExtras {
     pub(crate) lsp: Lsp,
     pub(crate) decorations: DecorationCollections,
+    pub(crate) range_decorations: DecorationCollections<RangeDecoration>,
     pub(crate) inline_completion: InlineCompletion,
     pub(crate) context_menu_content: ContextMenuContent,
     pub(crate) hover_popover: Option<HoverPopoverState>,
@@ -348,6 +355,7 @@ impl Default for EditorExtras {
         Self {
             lsp: Lsp::default(),
             decorations: DecorationCollections::default(),
+            range_decorations: DecorationCollections::default(),
             inline_completion: InlineCompletion::default(),
             context_menu_content: ContextMenuContent::default(),
             hover_popover: None,