Fix up runtime discovery with progress notification and improved user feedback (#9247)

Addresses #8404

With this PR, we now show a progress notification when users explicitly
call _Interpreter: Discover All Interpreters_. It looks like this while
discovery is going on (which can take a while, but if a user really
explicitly said to do this, probably the right option):

<img width="1368" height="994" alt="Screenshot 2025-09-01 at 3 20 49 PM"
src="https://github.com/user-attachments/assets/78ca42b0-38f5-4e79-a7ed-19a7dc26dec6"
/>

If nothing new is found, the progress notification resolves and then you
see this:

<img width="1368" height="994" alt="Screenshot 2025-09-01 at 3 21 04 PM"
src="https://github.com/user-attachments/assets/235a0614-e208-4eb4-98b7-5900d0e12573"
/>

If something new _is_ found, the progress notification resolves and then
you see this:

<img width="1368" height="994" alt="Screenshot 2025-09-01 at 3 22 41 PM"
src="https://github.com/user-attachments/assets/30aec486-28fd-4bde-835f-9f2764973439"
/>


### Release Notes

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#### New Features

- Improved user feedback when using the command _Interpreter: Discover
All Interpreters_.

#### Bug Fixes

- N/A


### QA Notes

The command _Interpreter: Discover All Interpreters_ will not run unless
the first round of discovery is done, which runs quietly in the
background. This may take longer than you expect. Once you _can_ run it:

- Look at all your interpreter options in Positron
- Add a new one via the regular terminal (for example, a new rig
version)
- Look at all your interpreter choices and see that your new one is not
there yet
- Execute the command, and note the new progress notification
- Look at all your interpreter choices and see that now the new one is
there
- Execute the command again, and see the same progress notification
- Note the message telling you nothing new was found

Author: juliasilge

src/vs/workbench/services/runtimeStartup/common/runtimeStartup.ts

@@ -19,6 +19,7 @@ import { ExtensionsRegistry } from '../../extensions/common/extensionsRegistry.j
 import { ExtensionIdentifier } from '../../../../platform/extensions/common/extensions.js';
 import { ILifecycleService, ShutdownReason } from '../../lifecycle/common/lifecycle.js';
 import { INotificationService, Severity } from '../../../../platform/notification/common/notification.js';
+import { IProgressService, ProgressLocation } from '../../../../platform/progress/common/progress.js';
 import { IWorkspaceTrustManagementService } from '../../../../platform/workspace/common/workspaceTrust.js';
 import { URI } from '../../../../base/common/uri.js';
 import { IWorkspaceContextService, WorkbenchState } from '../../../../platform/workspace/common/workspace.js';
@@ -128,6 +129,7 @@ export class RuntimeStartupService extends Disposable implements IRuntimeStartup
 		@ILogService private readonly _logService: ILogService,
 		@INotificationService private readonly _notificationService: INotificationService,
 		@IPositronNewFolderService private readonly _newFolderService: IPositronNewFolderService,
+		@IProgressService private readonly _progressService: IProgressService,
 		@IRuntimeSessionService private readonly _runtimeSessionService: IRuntimeSessionService,
 		@IStorageService private readonly _storageService: IStorageService,
 		@IWorkspaceContextService private readonly _workspaceContextService: IWorkspaceContextService,
@@ -662,39 +664,49 @@ export class RuntimeStartupService extends Disposable implements IRuntimeStartup
 			return;
 		}
 
-		// Set up event to notify when runtimes are added.
+		// Remember the old set of runtimes so we can report any new ones
 		const oldRuntimes = this._languageRuntimeService.registeredRuntimes;
-		this._register(
-			this._languageRuntimeService.onDidChangeRuntimeStartupPhase(
-				(phase) => {
+		this._logService.debug('[Runtime startup] Refreshing runtime discovery.');
+		this._discoveryCompleteByExtHostId.forEach((_, extHostId, m) => {
+			m.set(extHostId, false);
+		});
+
+		// Start progress for the discovery process
+		await this._progressService.withProgress({
+			location: ProgressLocation.Notification,
+			title: nls.localize('positron.runtimeStartupService.discoveringRuntimes', 'Discovering interpreters...'),
+			cancellable: false
+		}, async (progress) => {
+			// Start the discovery process
+			this.discoverAllRuntimes();
+
+			// Wait for discovery to complete
+			await new Promise<void>((resolve) => {
+				const disposable = this._languageRuntimeService.onDidChangeRuntimeStartupPhase(phase => {
 					if (phase === RuntimeStartupPhase.Complete) {
 						const newRuntimes = this._languageRuntimeService.registeredRuntimes;
 						const addedRuntimes = newRuntimes.filter(newRuntime => {
 							return !oldRuntimes.some(oldRuntime => {
 								return oldRuntime.runtimeId === newRuntime.runtimeId;
 							});
 						});
-
-						// If any runtimes were added, show a notification.
+						// Use addedRuntimes here and resolve the promise
 						if (addedRuntimes.length > 0) {
 							this._notificationService.info(nls.localize('positron.runtimeStartupService.runtimesAddedMessage',
 								"Found {0} new interpreter{1}: {2}.",
 								addedRuntimes.length,
 								addedRuntimes.length > 1 ? 's' : '',
 								addedRuntimes.map(runtime => { return runtime.runtimeName; }).join(', ')));
+						} else {
+							this._notificationService.info(nls.localize('positron.runtimeStartupService.noNewRuntimesMessage',
+								"No new interpreters found."));
 						}
+						resolve();
+						disposable.dispose();
 					}
-				}
-			)
-		);
-
-		this._logService.debug('[Runtime startup] Refreshing runtime discovery.');
-		this._discoveryCompleteByExtHostId.forEach((_, extHostId, m) => {
-			m.set(extHostId, false);
+				});
+			});
 		});
-
-		this.discoverAllRuntimes();
-
 	}
 
 	/**