Model host placeholders as route parameters

[42dknp]

Summary

• rename the public RouteMatch::$pathParameters property to routeParameters
• preserve both host- and path-derived placeholders as hydratable route parameters
• keep route parameters at the highest request-hydration precedence
• document that Router::generate() returns an origin-less URI reference
• add routing tests for dynamic host placeholders and host-/scheme-constrained URL generation
• record the canonical Route Parameter term in the package context glossary

This is an intentional pre-stable interface correction for the v0.1 package. Consumers using RouteMatch::$pathParameters or the corresponding named constructor argument must migrate to routeParameters.

Closes #4

Verification

• composer quality
• 133 tests, 249 assertions
• 100% line coverage (709/709 statements)
• PHPStan and formatting checks pass
• no dependency security advisories found