fix(amazonq): inline chat onReject should revert to initial document state (#8599)

## Problem


## Solution
simply revert to whatever document initial content is

---

- Treat all work as PUBLIC. Private `feature/x` branches will not be
squash-merged at release time.
- Your code changes must meet the guidelines in
[CONTRIBUTING.md](https://github.com/aws/aws-toolkit-vscode/blob/master/CONTRIBUTING.md#guidelines).
- License: I confirm that my contribution is made under the terms of the
Apache 2.0 license.

Author: Will-ShaoHua

packages/amazonq/.changes/next-release/Bug Fix-00d5a036-67d6-46fe-925b-48d55d647a3f.json

@@ -0,0 +1,4 @@
+{
+	"type": "Bug Fix",
+	"description": "fix: inline chat fails to revert to original state after users reject"
+}

packages/amazonq/src/inlineChat/controller/inlineChatController.ts

@@ -117,12 +117,14 @@ export class InlineChatController {
                 this.task
             )
         }
-        const insertions = task.diff.filter((diff) => diff.type === 'insertion')
+        // Revert to the original document text
+        const fullRange = new vscode.Range(
+            task.document.positionAt(0),
+            task.document.positionAt(task.document.getText().length)
+        )
         await editor.edit(
             (editBuilder) => {
-                for (const insertion of insertions) {
-                    editBuilder.delete(insertion.range)
-                }
+                editBuilder.replace(fullRange, task.originalDocumentText)
             },
             { undoStopAfter: false, undoStopBefore: false }
         )

packages/amazonq/src/inlineChat/controller/inlineTask.ts

@@ -47,6 +47,8 @@ export class InlineTask {
     public selectedText: string
     public languageName: string | undefined
 
+    public readonly originalDocumentText: string
+
     public partialSelectedText: string | undefined
     public partialSelectedTextRight: string | undefined
 
@@ -67,6 +69,7 @@ export class InlineTask {
     ) {
         this.selectedRange = textDocumentUtil.expandSelectionToFullLines(document, selection)
         this.selectedText = document.getText(this.selectedRange)
+        this.originalDocumentText = document.getText()
         this.languageName = extractLanguageNameFromFile(document)
     }