feat: add mock websocket requests

[cryptotavares]

Summary

The existing mock_network tool only intercepts HTTP requests. WebSocket connections — used heavily by dApps for real-time data (price feeds, order books, streaming state) — pass through unintercepted. This makes it impossible to test WebSocket-dependent flows without a live server, or to simulate specific server-to-client message sequences.

This PR adds a mock_websocket tool that intercepts WebSocket connections via Playwright's routeWebSocket API, enabling targeted message matching, scripted responses, and full connection lifecycle control.

Changes

New tool: mock_websocket

Mirrors the mock_network tool's action-based API (add, clear, list, messages) adapted for WebSocket semantics:

• Intercepts by exact URL — each mock targets a specific ws:// or wss:// endpoint (no wildcards, since WebSocket routing in Playwright uses exact URL matching)
• Rule-based message matching — incoming messages are matched against rules using substring inclusion (includes: string | string[]). Matched messages trigger scripted respond and/or followUpResponse payloads with optional delays
• Two connection modes: passthrough (default) connects to the real server and forwards unmatched messages; full mock mode (passthrough: false) operates without a real connection
• Connection lifecycle management — tracks active connections per URL; replacing a mock for the same URL closes stale connections and invalidates pending delayed responses via a generation counter
• Message recording — records all intercepted messages (client-to-server and server-to-client) with direction, timestamps, and matched rule IDs; capped at 500 records with configurable truncation

Architecture

Layer	Files	What
Types	tool-inputs.ts, tool-outputs.ts, errors.ts	WebSocketMockDefinition, WebSocketMockMessageRule, MockWebSocketInput/Result, MM_MOCK_WEBSOCKET_FAILED error code
Validation	schemas.ts	Zod schemas with URL protocol enforcement (ws:///wss:// only), wildcard rejection, exclusive mock/mocks constraint on add action
Core	mock-websocket.ts	WebSocketMockRouteManager class (per-BrowserContext via WeakMap) and mockWebSocketTool entry point
Registry	registry.ts	Registered as mock_websocket, categorized as mutating (tool count: 30 → 31)
CLI	mm.ts	mm mock-websocket {add,clear,list,messages} subcommands
Docs	README.md, SKILL.md	Tool table, CLI reference, error codes

Other changes

• mock-network tests: improved type narrowing in result assertions (replacing broad type checks with discriminated union narrowing via result.action)
• Coverage thresholds: adjusted branches, functions, and statements thresholds in vitest.config.mts to reflect the new code

Testing

Comprehensive test suite in mock-websocket.test.ts covering:

• All four actions (add/clear/list/messages)
• Full mock mode and passthrough mode
• Delayed responses and follow-up responses with timer ordering
• Mock replacement with socket closure and generation invalidation
• Stale timer cancellation across clear and replace scenarios
• Active connection tracking (including no-negative-count after clear)
• Message record retention limits
• Error handling for closed connections
• Schema validation tests for URL enforcement, wildcard rejection, and exclusive mock/mocks constraint