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/context.go

@@ -26,3 +26,25 @@ func User(ctx context.Context) (*Principal, bool) {
 	u, ok := ctx.Value(userKey{}).(*Principal)
 	return u, ok && u != nil
 }
+
+type credentialKey struct{}
+
+// WithCredential stores the resolved credential (e.g. *ApiToken) on ctx.
+func WithCredential(ctx context.Context, cred any) context.Context {
+	if ctx == nil {
+		ctx = context.Background()
+	}
+	return context.WithValue(ctx, credentialKey{}, cred)
+}
+
+// Credential returns the resolved credential from ctx.
+func Credential(ctx context.Context) (any, bool) {
+	if ctx == nil {
+		return nil, false
+	}
+	c := ctx.Value(credentialKey{})
+	if c == nil {
+		return nil, false
+	}
+	return c, true
+}