docs: fix additional comment typos across renderer and selection

Correct scrambled FIXME wording in InputHandler, "however" in
DomRenderer, duplicate "the" in selection code, "separate" and grammar
in DomRendererRowFactory, and "may cause" in WebglRenderer.

Co-authored-by: Cursor <cursoragent@cursor.com>

src/browser/services/SelectionService.ts

@@ -927,7 +927,7 @@ export class SelectionService extends Disposable implements ISelectionService {
     // Incremenet the end index so it is at the start of the next character
     endIndex++;
 
-    // Calculate the start _column_, converting the the string indexes back to
+    // Calculate the start _column_, converting the string indexes back to
     // column coordinates.
     let start =
       startIndex // The index of the selection's start char in the line string
@@ -935,7 +935,7 @@ export class SelectionService extends Disposable implements ISelectionService {
       - leftWideCharCount // The number of wide chars left of the initial char
       + leftLongCharOffset; // The number of additional chars left of the initial char added by columns with strings longer than 1 (emojis)
 
-    // Calculate the length in _columns_, converting the the string indexes back
+    // Calculate the length in _columns_, converting the string indexes back
     // to column coordinates.
     let length = Math.min(this._bufferService.cols, // Disallow lengths larger than the terminal cols
       endIndex // The index of the selection's end char in the line string