fix: nonlocal → global for module-level variables in challenge files

Three challenge files used `nonlocal` to reference module-level variables,
which is a SyntaxError. Module-level variables require `global` instead.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: travisjneuman

practice/challenges/intermediate/05-retry-decorator.py

@@ -39,7 +39,7 @@ def retry(max_retries: int = 3, base_delay: float = 0.1, exceptions: tuple = (Ex
 
     @retry(max_retries=3, base_delay=0.001)
     def always_works():
-        nonlocal call_count
+        global call_count
         call_count += 1
         return "ok"
 
@@ -51,7 +51,7 @@ def always_works():
 
     @retry(max_retries=5, base_delay=0.001)
     def works_third_try():
-        nonlocal attempt
+        global attempt
         attempt += 1
         if attempt < 3:
             raise ValueError("not yet")

practice/challenges/intermediate/13-async-fetcher.py

@@ -44,7 +44,7 @@ async def async_fetch_all(urls: list[str], fetch_func, max_concurrent: int = 5)
     current_simultaneous = 0
 
     async def fake_fetch(url: str) -> str:
-        nonlocal fetch_count, max_simultaneous, current_simultaneous
+        global fetch_count, max_simultaneous, current_simultaneous
         fetch_count += 1
         current_simultaneous += 1
         max_simultaneous = max(max_simultaneous, current_simultaneous)

practice/challenges/solutions/intermediate/05-retry-decorator-solution.py

@@ -37,7 +37,7 @@ def wrapper(*args, **kwargs):
 
     @retry(max_retries=3, base_delay=0.001)
     def always_works():
-        nonlocal call_count
+        global call_count
         call_count += 1
         return "ok"
 
@@ -48,7 +48,7 @@ def always_works():
 
     @retry(max_retries=5, base_delay=0.001)
     def works_third_try():
-        nonlocal attempt
+        global attempt
         attempt += 1
         if attempt < 3:
             raise ValueError("not yet")

practice/challenges/solutions/intermediate/13-async-fetcher-solution.py

@@ -34,7 +34,7 @@ async def limited_fetch(url: str) -> str:
     current_simultaneous = 0
 
     async def fake_fetch(url: str) -> str:
-        nonlocal fetch_count, max_simultaneous, current_simultaneous
+        global fetch_count, max_simultaneous, current_simultaneous
         fetch_count += 1
         current_simultaneous += 1
         max_simultaneous = max(max_simultaneous, current_simultaneous)