Add documentation and targeted configuration for ESLint rule

Author: Copilot

.eslintrc.context.js

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+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+'use strict';
+
+const RULES_DIR = require('eslint-plugin-rulesdir');
+RULES_DIR.RULES_DIR = './build/eslint-rules';
+
+module.exports = {
+	extends: ['.eslintrc.base.json'],
+	env: {
+		browser: true,
+		node: true
+	},
+	parserOptions: {
+		project: 'tsconfig.eslint.json'
+	},
+	plugins: ['rulesdir'],
+	overrides: [
+		{
+			files: ['webviews/common/context.tsx'],
+			rules: {
+				'rulesdir/public-methods-well-defined-types': 'error'
+			}
+		}
+	]
+};

build/eslint-rules/README.md

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+# Local ESLint Rules
+
+This directory contains custom ESLint rules specific to this repository.
+
+## public-methods-well-defined-types
+
+This rule enforces that public methods in exported classes return well-defined types (no inline types).
+
+### Rule Details
+
+- **Purpose**: Ensure public methods return named interfaces, types, or classes instead of inline object literals or anonymous types
+- **Scope**: Applies only to `webviews/common/context.tsx`
+- **Level**: Error
+
+### Examples
+
+**Incorrect** (will trigger the rule):
+```typescript
+export class MyClass {
+	public badMethod(): { foo: string; bar: number } {
+		return { foo: 'test', bar: 123 };
+	}
+
+	public badUnionMethod(): string | { error: string } {
+		return 'test';
+	}
+}
+```
+
+**Correct** (will not trigger the rule):
+```typescript
+interface ResultType {
+	foo: string;
+	bar: number;
+}
+
+export class MyClass {
+	public goodMethod(): ResultType {
+		return { foo: 'test', bar: 123 };
+	}
+
+	public goodPromiseMethod(): Promise<string> {
+		return Promise.resolve('test');
+	}
+
+	// Private methods are not checked
+	private privateMethod(): { foo: string } {
+		return { foo: 'test' };
+	}
+}
+```
+
+### Configuration
+
+To use this rule, include it in your ESLint configuration:
+
+```javascript
+const RULES_DIR = require('eslint-plugin-rulesdir');
+RULES_DIR.RULES_DIR = './build/eslint-rules';
+
+module.exports = {
+	plugins: ['rulesdir'],
+	rules: {
+		'rulesdir/public-methods-well-defined-types': 'error'
+	}
+};
+```
+
+### Testing
+
+Use `.eslintrc.context.js` to test the rule on the target file:
+
+```bash
+npx eslint --config .eslintrc.context.js webviews/common/context.tsx
+```