Vale v0.1.6

• Added an embedded GatewayBuilder component example module.
• Switched CI to a per-module test/lint/vet matrix for root, optional modules, and examples.
• Documented public API tiers for stable root APIs, DTO boundaries, advanced packages, optional modules, and binary assembly.
• Reduced route cache miss work by reusing computed route match cache keys.
• Removed avoidable allocations in single-route entrypoint fast-path and route cache eligibility checks.
• Stabilized reload health checking by running an immediate health pass on health checker start and avoiding test port reuse races.