fix: Python 3.9 compatibility and pytest config

- Add 'from __future__ import annotations' to 3 files using X | None
  union syntax (PEP 604 requires Python 3.10+; deferred evaluation
  makes it safe on 3.9)
- Replace unsupported collect_ignore_glob with norecursedirs in
  [tool.pytest.ini_options] (collect_ignore_glob is not a valid
  pyproject.toml pytest key, causing PytestConfigWarning)

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: DevOpsDerek

03_process_management/kill_process.py

@@ -9,6 +9,8 @@
   - Safety patterns: dry-run mode, confirmation, protected list
 """
 
+from __future__ import annotations
+
 import time
 
 import psutil  # pip install psutil

exercises/03_disk_alert/solution.py

@@ -2,6 +2,8 @@
 Exercise 03 — Disk Space Alert  ✅ SOLUTION
 """
 
+from __future__ import annotations
+
 import sys
 
 import psutil

exercises/10_health_snapshot/solution.py

@@ -2,6 +2,8 @@
 Exercise 10 — System Health Snapshot  ✅ SOLUTION
 """
 
+from __future__ import annotations
+
 import json
 import socket
 from datetime import datetime

pyproject.toml

@@ -49,7 +49,7 @@ exclude = [
 known-third-party = ["psutil", "schedule"]
 
 [tool.pytest.ini_options]
-testpaths    = ["tests"]
-addopts      = "-v --tb=short"
-# Ignore exercise starter files — they contain intentional incomplete code
-collect_ignore_glob = ["exercises/*/exercise.py"]
+testpaths = ["tests"]
+addopts   = "-v --tb=short"
+# Exercise starter files contain intentional incomplete code — don't collect them
+norecursedirs = ["exercises"]