v0.4.2

v0.4.2 - Dashboard Stability (Epic 9)

Fix file descriptor and goroutine leaks in dashboard watch mode that caused
"too many open files" errors after extended runtime.

Changes:

• fix: explicit watcher cleanup for macOS kqueue FD release (Story 9.1)
• feat: refactor dashboard to subscription model (Story 9.2)
• feat: add stress tests for FD/goroutine leak detection (Story 9.3)

The dashboard now uses a subscription model with single long-lived goroutines
per watcher instead of command chaining, preventing resource accumulation.

New: make test-stress target for regression testing.