Fix #openPullRequest to detect PRs from diff views with multi-workspace support and use consistent terminology (#7803)

* Initial plan

* Fix #openPullRequest to consider diff editors and use consistent terminology

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

* Implement diff view detection for #openPullRequest tool

Check if active editor is showing PR diff content (either pr: or review: scheme) and determine the associated PR. This addresses the feedback to detect PRs from diff views instead of just checking for checked out PRs.

* Use Tab API to detect diff editors in #openPullRequest tool

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

* Use reviewParams rootUri to find correct folder manager

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

* Revert proposal changes

Author: Copilot

src/lm/tools/openPullRequestTool.ts

@@ -4,6 +4,7 @@
  *--------------------------------------------------------------------------------------------*/
 
 import * as vscode from 'vscode';
+import { fromPRUri, fromReviewUri, Schemes } from '../../common/uri';
 import { PullRequestModel } from '../../github/pullRequestModel';
 import { PullRequestOverviewPanel } from '../../github/pullRequestOverview';
 import { PullRequestTool } from './activePullRequestTool';
@@ -12,10 +13,58 @@ export class OpenPullRequestTool extends PullRequestTool {
 	public static readonly toolId = 'github-pull-request_openPullRequest';
 
 	protected _findActivePullRequest(): PullRequestModel | undefined {
-		return PullRequestOverviewPanel.currentPanel?.getCurrentItem();
+		// First check if there's a PR overview panel open
+		const panelPR = PullRequestOverviewPanel.currentPanel?.getCurrentItem();
+		if (panelPR) {
+			return panelPR;
+		}
+
+		// Check if the active tab is a diff editor showing PR content
+		const activeTab = vscode.window.tabGroups.activeTabGroup.activeTab;
+		if (activeTab?.input instanceof vscode.TabInputTextDiff) {
+			const diffInput = activeTab.input;
+			const urisToCheck = [diffInput.original, diffInput.modified];
+
+			for (const uri of urisToCheck) {
+				if (uri.scheme === Schemes.Pr) {
+					// This is a PR diff from GitHub
+					const prParams = fromPRUri(uri);
+					if (prParams) {
+						return this._findPullRequestByNumber(prParams.prNumber, prParams.remoteName);
+					}
+				} else if (uri.scheme === Schemes.Review) {
+					// This is a review diff from a checked out PR
+					const reviewParams = fromReviewUri(uri.query);
+					if (reviewParams) {
+						// For review scheme, find the folder manager based on the root path
+						const rootUri = vscode.Uri.file(reviewParams.rootPath);
+						const folderManager = this.folderManagers.getManagerForFile(rootUri);
+						return folderManager?.activePullRequest;
+					}
+				}
+			}
+		}
+
+		return undefined;
+	}
+
+	private _findPullRequestByNumber(prNumber: number, remoteName: string): PullRequestModel | undefined {
+		for (const manager of this.folderManagers.folderManagers) {
+			for (const repo of manager.gitHubRepositories) {
+				if (repo.remote.remoteName === remoteName) {
+					// Look for the PR in the repository's PR cache
+					for (const pr of repo.pullRequestModels) {
+						if (pr.number === prNumber) {
+							return pr;
+						}
+					}
+				}
+			}
+		}
+		return undefined;
 	}
 
 	protected _confirmationTitle(): string {
 		return vscode.l10n.t('Open Pull Request');
 	}
-}
+}