v0.4.1-rc2

Phase 4 release candidate 2.\n\nHighlights:\n- Native Electron agent client with bounded working context and dynamic tool routing.\n- Structured-first desktop and browser execution with bounded native-vision fallback.\n- Browser element lifecycle, stale-reference recovery, and deterministic browser-session startup.\n- Strict completion evidence and actionable recovery guidance.\n- Computer MCP execution skill for efficient, state-aware model behavior.\n\nValidated with Agent Runtime, client, unit, desktop integration, browser E2E, MCP E2E, and production client build suites.