Route parameter type coercion

[philipobenito]

Automatically coerce route parameters from strings to typed values based on pattern matchers or explicit configuration.

Current behaviour:
All route variables are strings, even when matched by typed patterns like {id:number}.

Proposed behaviour:

$router->map('GET', '/users/{id:number}', function (ServerRequestInterface $request, array $args) {
    // $args['id'] is now an int, not a string
});

Considerations:

• This is a breaking change to the variable presentation contract
• Needs careful design around what types are supported (int, float, bool)
• Should respect the pattern matcher type (:number implies int)
• Could be opt-in via strategy or router configuration
• Interacts with the parameter injection feature (Inject route parameters as controller method arguments #356)

Target: 7.x