…CPU on terminal close (#114)

* fix: restore signal handlers to prevent 100% CPU on terminal close

When the IDE terminal is closed without stopping the framework first,
the PTY is destroyed and workers become orphaned with broken
STDIN/STDOUT/STDERR. Without proper signal handlers (SIGHUP/SIGINT/
SIGTERM), workers cannot shut down gracefully.

Changes:
- installSignal(): uncomment all signal handlers (SIGINT, SIGTERM,
  SIGHUP, SIGQUIT, SIGUSR2, SIGIO, SIGPIPE). This is called from
  runAll() for the master process.
- reinstallSignal(): properly reinstall signal handlers via event
  loop after fork, replacing the previous no-op implementation.
  Workers now respond to SIGHUP (terminal close) by stopping
  gracefully via Workerman::signalHandler().
- runAll(): enable installSignal() call that was previously
  commented out.
- Add Workerman\Events\EventInterface import required by the
  reinstalled signal handlers.

* chore: update PHP version support to 8.5 and modernize dev tooling

- Add PHP 8.5 to version constraint
- Bump php-cs-fixer from ^3.2 to ^3.64 (compatible with PHP 8.4+)
- Bump phpstan from ^1.1 to ^1.12
- Bump swoole/ide-helper from ~4.4.0 to ~5.0
- Widen symfony/var-dumper constraint to ^5.3 || ^6.0 || ^7.0
- CI: bump coding-style PHP 8.0 → 8.3
- CI: bump static-analysis PHP 7.4 → 8.3
- CI: test matrix updated to 8.1, 8.2, 8.3, 8.4 (drop EOL 7.4/8.0)
- Regenerate composer.lock with updated deps

* chore: update CI actions to resolve deprecation warnings

- actions/checkout@v2 → @v4 (Node.js 20 deprecated, v4 uses Node.js 24)
- fkirc/skip-duplicate-actions@v4 → @v5 (set-output deprecated)