[P3] Model host placeholders as route parameters and clarify URL generation #4

Problem

Symfony route matching returns both path placeholders and host placeholders as application route parameters. SymfonyRouter intentionally keeps every non-internal matcher value, so a route such as {tenant}.api.example.test/reports/{reportId} currently produces:

$match->pathParameters === [
    "reportId" => "42",
    "tenant" => "acme",
];

Both values are then available to request hydration and override query/body values. This is useful behavior, but the public name pathParameters incorrectly implies that every value originates in the URI path.

URL generation has a related intentional invariant: Router::generate() returns an origin-less reference such as /reports/42; scheme and host are removed even for host-constrained routes.

Proposed direction

Before a stable release, model these values as route parameters rather than path parameters. Prefer renaming the public property to routeParameters; if compatibility must be preserved, provide a documented migration or deprecation path.

Acceptance criteria

• Host and path placeholders remain hydratable route parameters.
• The public model no longer mislabels host-derived values as path-only values.
• Tests cover a route with both a host placeholder and path placeholder.
• Hydration precedence for route parameters over query and body is documented.
• The origin-less return contract of Router::generate() is documented and tested for host- and scheme-constrained routes.