feat: transitive dependency resolution

Resolver now pulls in transitive dependencies automatically.
Declaring 'packages { root {} }' where root→mid→leaf resolves
all three packages in correct topological order. Previously
every package had to be listed explicitly in the config.

build_registry pre-populates from $KAPPA_ROOT/cache/packages/
so transitive deps can be found without remote fetching.

src/main.cpp

@@ -111,6 +111,24 @@ static void handle_parse_error(const char* path,
 static resolve::Registry build_registry(const dsl::SystemConfig& cfg) {
     resolve::Registry registry;
 
+    // Pre-populate from cached packages so transitive deps can be resolved
+    auto pkg_dir = paths::packages_dir();
+    std::error_code ec;
+    if (std::filesystem::exists(pkg_dir)) {
+        for (auto& entry : std::filesystem::directory_iterator(pkg_dir, ec)) {
+            if (ec) break;
+            if (entry.path().extension() != ".kap") continue;
+            std::ifstream in(entry.path());
+            if (!in) continue;
+            std::ostringstream buf;
+            buf << in.rdbuf();
+            try {
+                auto pkg = dsl::parse(buf.str());
+                registry.try_emplace(pkg.name, std::move(pkg));
+            } catch (...) { continue; }
+        }
+    }
+
     for (const auto& pref : cfg.packages) {
         bool found = false;
 

src/resolve/plan.cpp

@@ -42,7 +42,58 @@ BuildPlan resolve(const dsl::SystemConfig& cfg, const Registry& registry) {
         nodes.push_back(std::move(step));
     }
 
-    // Detect conflicts between selected packages
+    // Transitive dependency discovery: pull in deps that are in the
+    // registry but not yet in the plan.  Continue until no new deps
+    // are discovered — handles arbitrarily deep dependency chains.
+    bool changed = true;
+    while (changed) {
+        changed = false;
+        std::size_t current_size = nodes.size();
+
+        for (std::size_t i = 0; i < current_size; ++i) {
+            if (!nodes[i].package) continue;
+
+            for (auto& dep : nodes[i].package->depends) {
+                if (name_to_idx.contains(dep.name)) continue;
+
+                // Skip feature-conditional deps that aren't enabled
+                if (!dep.feature.empty()) {
+                    auto fit = nodes[i].resolved.features.find(dep.feature);
+                    if (fit == nodes[i].resolved.features.end() || !fit->second.enabled) {
+                        continue;
+                    }
+                }
+
+                auto rit = registry.find(dep.name);
+                if (rit == registry.end()) continue;
+
+                auto& pkg = rit->second;
+                auto resolved = config::resolve_package(pkg, cfg.system, {});
+
+                BuildStep step;
+                step.name         = pkg.name;
+                step.package      = &pkg;
+                step.resolved     = std::move(resolved);
+                step.enabled_init = cfg.boot.init;
+
+                for (auto& ddep : pkg.depends) {
+                    if (!ddep.feature.empty()) {
+                        auto fit = step.resolved.features.find(ddep.feature);
+                        if (fit == step.resolved.features.end() || !fit->second.enabled) {
+                            continue;
+                        }
+                    }
+                    step.dependencies.push_back({ddep.name, ddep.version});
+                }
+
+                name_to_idx[step.name] = nodes.size();
+                nodes.push_back(std::move(step));
+                changed = true;
+            }
+        }
+    }
+
+    // Detect conflicts between all selected packages (including transitive)
     std::unordered_set<std::string> selected;
     for (auto& node : nodes) { selected.insert(node.name); }