docs(build): document dependency package setup

docs/superpowers/plans/2026-07-29-fesa-phase-1.md

@@ -251,9 +251,11 @@ git commit -m "build: bootstrap FESA CMake project"
 - Create: `include/fesa/core/vec3.hpp`
 - Create: `include/fesa/core/source_location.hpp`
 - Create: `include/fesa/core/diagnostic.hpp`
+- Create: `include/fesa/core/status.hpp`
 - Create: `tests/unit/core/entity_id_test.cpp`
 - Create: `tests/unit/core/vec3_test.cpp`
 - Create: `tests/unit/core/diagnostic_test.cpp`
+- Create: `tests/unit/core/status_test.cpp`
 - Modify: `CMakeLists.txt`
 - Modify: `tests/CMakeLists.txt`
 
@@ -283,21 +285,28 @@ struct SourceLocation final {
 };
 
 enum class DiagnosticStage {
-    io, lexical, syntax, semantic, model, equation, solver, results
+    io, syntax, semantic, model, equation, solver, results, validation
 };
 
+enum class Severity { warning, error };
+
 struct Diagnostic final {
     DiagnosticStage stage;
+    Severity severity;
     std::string code;
     std::string message;
     std::optional<SourceLocation> source;
-    std::optional<std::int64_t> entity_id;
+};
+
+struct Status final {
+    bool succeeded;
+    std::vector<Diagnostic> diagnostics;
 };
 ```
 
 - [ ] **Step 1: Write failing tests**
 
-Cover negative/zero entity-ID rejection, typed-ID non-interchangeability at compile time, finite `Vec3` validation, and full diagnostic context preservation.
+Cover negative entity-ID rejection, typed-ID non-interchangeability at compile time, finite `Vec3` validation, full diagnostic context preservation, and success/failure status preservation.
 
 - [ ] **Step 2: Run focused tests and confirm compile or assertion failure**