Address PR feedback: use constants, clarify watcher code, add AGENTS.md

- addService.ts: Use SUPPORTED_LANGUAGES constant instead of hardcoded array
- RevealStep.ts: Extract l10n strings to constants before comparison
- FileSystemWatcherService.ts: Add clarifying comments for watcher registration flow
- AGENTS.md: Add agent development guide per Jeffrey's suggestion

Author: spboyer

ext/vscode/AGENTS.md

@@ -0,0 +1,61 @@
+# Agent Development Guide
+
+A file for [guiding coding agents](https://agents.md/).
+
+## Commands
+
+- **Install dependencies:** `npm install`
+- **Build:** `npm run build`
+- **Lint:** `npm run lint`
+- **Spell Check:** `npx cspell "src/**/*.ts"`
+- **Unit Tests:** `npm run unit-test`
+- **Watch mode:** `npm run watch`
+- **Package extension:** `npm run package`
+
+## Directory Structure
+
+- Extension entry point: `src/extension.ts`
+- Commands: `src/commands/`
+- Language features: `src/language/` (IntelliSense, diagnostics, etc.)
+- Views & tree providers: `src/views/`
+- Utilities: `src/utils/`
+- Tests: `src/test/`
+- Constants: `src/constants/`
+- Services: `src/services/`
+
+## Pre-Commit Checklist
+
+1. Run `npm run lint` and fix all issues
+2. Run `npx cspell "src/**/*.ts"` and fix spelling errors
+3. Run `npm run unit-test` and ensure all tests pass
+4. Update README.md if functionality changed
+5. Verify no merge conflict markers in code
+
+## Code Conventions
+
+### Copyright Headers
+All TypeScript source files MUST include the Microsoft copyright header:
+```typescript
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT License.
+```
+
+### Localization
+- All user-facing strings shown in the UI, error messages, etc. must use `vscode.l10n.t()`
+- All user-facing strings in package.json must be extracted into package.nls.json
+
+### UI Best Practices
+- Instead of `vscode.window.showQuickPick`, use `IActionContext.ui.showQuickPick`
+- Instead of `vscode.window.showInputBox`, use `IActionContext.ui.showInputBox`
+- Same for `showWarningMessage`, `showOpenDialog`, and `showWorkspaceFolderPick`
+
+### Resource Management
+- FileSystemWatchers are a scarce resource on some systems - use the shared `FileSystemWatcherService`
+- Dispose resources properly using `vscode.Disposable` pattern
+- Use `ExtensionContext.subscriptions` for cleanup
+
+### Testing
+- Use Mocha for test framework
+- Use Chai for assertions
+- Mock VS Code APIs using Sinon
+- Keep tests focused and isolated

ext/vscode/src/commands/addService.ts

@@ -4,6 +4,7 @@
 import { IActionContext } from '@microsoft/vscode-azext-utils';
 import * as vscode from 'vscode';
 import * as yaml from 'yaml';
+import { SUPPORTED_LANGUAGES } from '../constants/languages';
 import { AzureDevCliModel } from '../views/workspace/AzureDevCliModel';
 
 /**
@@ -50,7 +51,7 @@ export async function addService(context: IActionContext, node?: AzureDevCliMode
 
     // Prompt for programming language
     const language = await context.ui.showQuickPick(
-        ['python', 'js', 'ts', 'csharp', 'java', 'go'].map(lang => ({ label: lang })),
+        SUPPORTED_LANGUAGES.map(lang => ({ label: lang })),
         { placeHolder: vscode.l10n.t('Select programming language') }
     );
 

ext/vscode/src/commands/azureWorkspace/wizard/RevealStep.ts

@@ -25,14 +25,16 @@ export class RevealStep extends AzureWizardExecuteStep<RevealResourceWizardConte
 
         // If reveal failed, show a helpful message with actions
         if (result === undefined) {
+            const copyResourceIdOption = vscode.l10n.t('Copy Resource ID');
+            const openInPortalOption = vscode.l10n.t('Open in Portal');
             const selection = await vscode.window.showInformationMessage(
                 vscode.l10n.t('Unable to reveal resource in tree. Resource ID: {0}', azureResourceId),
-                vscode.l10n.t('Copy Resource ID'),
-                vscode.l10n.t('Open in Portal')
+                copyResourceIdOption,
+                openInPortalOption
             );
-            if (selection === vscode.l10n.t('Copy Resource ID')) {
+            if (selection === copyResourceIdOption) {
                 await vscode.env.clipboard.writeText(azureResourceId);
-            } else if (selection === vscode.l10n.t('Open in Portal')) {
+            } else if (selection === openInPortalOption) {
                 await vscode.commands.executeCommand('azureResourceGroups.openInPortal', azureResourceId);
             }
         }

ext/vscode/src/services/FileSystemWatcherService.ts

@@ -20,6 +20,7 @@ export class FileSystemWatcherService implements vscode.Disposable {
         let watcherEntry = this.watchers.get(pattern);
 
         if (!watcherEntry) {
+            // Create new watcher and entry for this pattern
             const watcher = vscode.workspace.createFileSystemWatcher(pattern);
             watcherEntry = {
                 watcher,
@@ -28,6 +29,7 @@ export class FileSystemWatcherService implements vscode.Disposable {
             this.watchers.set(pattern, watcherEntry);
 
             // Set up forwarding events to all listeners
+            // Note: watcherEntry is captured in closure and will include all future listeners
             watcher.onDidChange(uri => {
                 watcherEntry!.listeners.forEach(listener => listener(uri));
             });
@@ -39,6 +41,7 @@ export class FileSystemWatcherService implements vscode.Disposable {
             });
         }
 
+        // Add callback to listeners (whether entry is new or existing)
         watcherEntry.listeners.add(callback);
 
         return {