Set up comprehensive frontend testing infrastructure

- Install Jest for unit testing with React Testing Library
- Install Playwright for end-to-end testing
- Configure Jest with proper TypeScript support and module mapping
- Create test setup files and utilities for both unit and e2e tests

Components:
* Jest configuration with coverage thresholds
* Playwright configuration with browser automation
* Unit tests for LoginForm, AuthContext, and useSocketIO hook
* E2E tests for authentication, dashboard, and agents workflows
* GitHub Actions workflow for automated testing
* Mock data and API utilities for consistent testing
* Test documentation with best practices

Testing features:
- Unit tests with 70% coverage threshold
- E2E tests with API mocking and user journey testing
- CI/CD integration for automated test runs
- Cross-browser testing support with Playwright
- Authentication system testing end-to-end

🚀 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

frontend/node_modules/parse5/dist/cjs/tokenizer/preprocessor.d.ts

@@ -0,0 +1,36 @@
+import { ERR, type ParserError, type ParserErrorHandler } from '../common/error-codes.js';
+export declare class Preprocessor {
+    private handler;
+    html: string;
+    pos: number;
+    private lastGapPos;
+    private gapStack;
+    private skipNextNewLine;
+    lastChunkWritten: boolean;
+    endOfChunkHit: boolean;
+    bufferWaterline: number;
+    private isEol;
+    private lineStartPos;
+    droppedBufferSize: number;
+    line: number;
+    constructor(handler: {
+        onParseError?: ParserErrorHandler | null;
+    });
+    /** The column on the current line. If we just saw a gap (eg. a surrogate pair), return the index before. */
+    get col(): number;
+    get offset(): number;
+    getError(code: ERR, cpOffset: number): ParserError;
+    private lastErrOffset;
+    private _err;
+    private _addGap;
+    private _processSurrogate;
+    willDropParsedChunk(): boolean;
+    dropParsedChunk(): void;
+    write(chunk: string, isLastChunk: boolean): void;
+    insertHtmlAtCurrentPos(chunk: string): void;
+    startsWith(pattern: string, caseSensitive: boolean): boolean;
+    peek(offset: number): number;
+    advance(): number;
+    private _checkForProblematicCharacters;
+    retreat(count: number): void;
+}