feat(06-01): grow router verbs, factories, and guard registry

- Add Post/Put/Patch/Delete on pact.Router and surf Router/Group
- Resolve name:param middleware via RegisterMiddlewareFactory
- Add bouncer.Registry with Guard, CredentialGuard, UnauthorizedWriter
- Re-express jwt as NewJWTGuard without changing Middleware bodies

bouncer/guard.go

@@ -0,0 +1,25 @@
+package bouncer
+
+import "net/http"
+
+// Guard resolves the caller's Principal for r, or an error describing why not.
+type Guard interface {
+	Authenticate(r *http.Request) (*Principal, error)
+}
+
+// CredentialGuard resolves the Principal AND its underlying credential (e.g.
+// *models.ApiToken) in one pass -- a DB-backed guard must never verify twice
+// per request (RESEARCH.md Pitfall 5: last_used_at must stamp once).
+type CredentialGuard interface {
+	AuthenticateCredential(r *http.Request) (*Principal, any, error)
+}
+
+// UnauthorizedWriter lets a guard write its own failure response. jwtGuard
+// implements this (reusing write401's {"error":true,"message":...} shape).
+// TokenGuard does NOT implement it: PHP's TokenScope, not ApiTokenGuard, owns
+// the {"error":"Invalid token"} 401 body (D-08) -- Registry.Middleware must
+// pass an unauthenticated request through untouched when a guard has no
+// UnauthorizedWriter, leaving denial to downstream middleware.
+type UnauthorizedWriter interface {
+	WriteUnauthorized(w http.ResponseWriter, err error)
+}