fix: oracle review fixes — resolver exit code, dead include, pointer compose

- Exit code: plan.missing.empty() ? 0 : 1 (was always returning 0)
- Removed dead <algorithm> include from plan.cpp
- BuildStep now composes config::ResolvedPackage instead of duplicating
  features/config fields; PackageDef stored as const pointer

src/resolve/plan.cpp

@@ -1,7 +1,6 @@
 #include "kappa/resolve/plan.hpp"
 #include "kappa/config/merge.hpp"
 
-#include <algorithm>
 #include <queue>
 
 namespace kappa::resolve {
@@ -23,15 +22,14 @@ BuildPlan resolve(const dsl::SystemConfig& cfg, const Registry& registry) {
 
         BuildStep step;
         step.name     = pkg.name;
-        step.package  = pkg;
-        step.features = resolved.features;
-        step.config   = resolved.config;
+        step.package  = &pkg;
+        step.resolved = std::move(resolved);
 
         for (auto& dep : pkg.depends) {
             if (!dep.feature.empty()) {
-                auto fit = step.features.find(dep.feature);
-                if (fit == step.features.end() || !fit->second.enabled) {
-                    continue; // feature-gated and disabled
+                auto fit = step.resolved.features.find(dep.feature);
+                if (fit == step.resolved.features.end() || !fit->second.enabled) {
+                    continue;
                 }
             }
             step.dependencies.push_back({dep.name, dep.version});