Fix file-scoped comments failing with "Error: File has been deleted" (#8664)

* Initial plan

* Initial analysis

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* Fix file-scoped comment failing with "Error: File has been deleted"

When creating a file-scoped comment (range is undefined), the
createReviewThread method was passing `line: 0` to the GitHub GraphQL
API. The API does not accept line 0 and returns a null thread, which
caused the misleading "File has been deleted" error.

Fix: pass endLine directly (undefined for file-scoped comments) instead
of converting undefined to 0. The line parameter is not required when
subjectType is FILE.

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* Remove file-scoped comment test that only tests mocks

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---------

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Co-authored-by: alexr00 <38270282+alexr00@users.noreply.github.com>

Author: Copilot

src/@types/vscode.proposed.chatSessionsProvider.d.ts

@@ -343,7 +343,7 @@ declare module 'vscode' {
 		/**
 		 * Statistics about the chat session.
 		 */
-		changes?: readonly ChatSessionChangedFile[] | readonly ChatSessionChangedFile2[];
+		changes?: readonly ChatSessionChangedFile[];
 
 		/**
 		 * Arbitrary metadata for the chat session. Can be anything, but must be JSON-stringifyable.
@@ -353,34 +353,7 @@ declare module 'vscode' {
 		metadata?: { readonly [key: string]: any };
 	}
 
-	/**
-	 * @deprecated Use `ChatSessionChangedFile2` instead
-	 */
 	export class ChatSessionChangedFile {
-		/**
-		 * URI of the file.
-		 */
-		modifiedUri: Uri;
-
-		/**
-		 * File opened when the user takes the 'compare' action.
-		 */
-		originalUri?: Uri;
-
-		/**
-		 * Number of insertions made during the session.
-		 */
-		insertions: number;
-
-		/**
-		 * Number of deletions made during the session.
-		 */
-		deletions: number;
-
-		constructor(modifiedUri: Uri, insertions: number, deletions: number, originalUri?: Uri);
-	}
-
-	export class ChatSessionChangedFile2 {
 		/**
 		 * URI of the file.
 		 */
@@ -728,9 +701,18 @@ declare module 'vscode' {
 	export interface ChatSessionInputState {
 		/**
 		 * Fired when the input state is changed by the user.
+		 *
+		 * Move to controller?
 		 */
 		readonly onDidChange: Event<void>;
 
+		/**
+		 * The resource associated with this chat session.
+		 *
+		 * This is `undefined` for chat sessions that have not yet started.
+		 */
+		readonly sessionResource: Uri | undefined;
+
 		/**
 		 * The groups of options to show in the UI for user input.
 		 *

src/github/pullRequestModel.ts

@@ -751,7 +751,7 @@ export class PullRequestModel extends IssueModel<PullRequest> implements IPullRe
 					pullRequestId: this.graphNodeId,
 					pullRequestReviewId: pendingReviewId,
 					startLine: startLine === endLine ? undefined : startLine,
-					line: (endLine === undefined) ? 0 : endLine,
+					line: endLine,
 					side,
 					subjectType: (startLine === undefined || endLine === undefined) ? SubjectType.FILE : SubjectType.LINE
 				}