Verify each finding against the current code and only fix it if needed.

Inline comments:
In `@src/Cookie/Contracts/CookieStorageInterface.php`:
- Around line 54-59: Add an explicit void return type to the interface method
flush() in CookieStorageInterface so it matches set(): void and delete(): void
and the implementing class Cookie::flush(): void; update the method signature
from "public function flush();" to include ": void" to ensure consistency
between the interface and its implementation.

In `@src/Session/Contracts/SessionStorageInterface.php`:
- Around line 42-59: Update the SessionStorageInterface by adding explicit ":
void" return types to its method signatures for set(), delete(), and flush() so
they match the implemented signatures (and other interfaces like ConfigInterface
and DebuggerStoreInterface); modify the declarations in SessionStorageInterface
(methods set(string $key, $value), delete(string $key), flush()) to include the
void return type to enforce the contract consistency with the implementations in
SessionTrait.

Verify each finding against the current code and only fix it if needed.

Nitpick comments:
In `@src/Cookie/Contracts/CookieStorageInterface.php`:
- Around line 25-29: The interface method all() currently returns mixed; tighten
its return type to array by changing the CookieStorageInterface::all() signature
to return array, update its docblock accordingly, and then update every
implementing class (implementations of CookieStorageInterface) to match the new
return type on their all() methods, adjusting any callers or tests that relied
on mixed to accept/expect an array; ensure method signatures remain compatible
with PHP return type rules and run static checks/tests to catch any mismatches.