feat: enable patrol develop on web and harden MCP session

[piotruela]

Summary

Web develop mode

• Implements patrol develop for web targets — previously blocked. Cold-starts the app on each restart since the web runner can't hot-restart like mobile (web_test_backend.dart, develop.ts, develop_service.dart).
• Forwards PATROL_LOG entries from the web runner to MCP so test status is observable in develop mode.
• Adds a timeout to npm/playwright install so a stalled install fails fast instead of hanging the backend.

MCP improvements

• Adds web screenshot support via Chrome DevTools Protocol, with a 10s WebSocket timeout so a non-responsive browser can't hang the tool (screenshot_service.dart).
• Surfaces test failure details (error messages, stack traces) in MCP status output instead of just a pass/fail flag (patrol_session.dart).
• Extracts platform-specific session logic (mobile vs. web exit semantics, stale-callback suppression) into a PlatformSessionBehavior abstraction (platform_session_behavior.dart).
• Hardens the hot-restart flag with an epoch counter so overlapping restarts can't prematurely lift suppression for each other.

E2E app / tooling

• Splits the web clipboard test and adds a new key-press test (web_example_key_press_test.dart, web_example_clipboard_test.dart).
• Adds MCP config files for the e2e app and a run-patrol helper.

[gemini-code-assist]

Code Review

This pull request introduces web support for the Patrol MCP server and enhances the develop command for web platforms. Key changes include implementing platform-specific session behaviors, adding web screenshot capabilities via the Chrome DevTools Protocol, and improving log surfacing and error handling for web tests. Additionally, the PR includes new web integration tests and updates to the patrol_cli to manage web-specific processes and debugger ports. Feedback includes a critical fix for invalid Dart syntax in patrol_session.dart, a recommendation to remove local absolute paths from configuration files, and suggestions to improve the robustness of WebSocket connections and hot restart suppression logic.