Steps 284-289: Phase 10e — environment layer, host boundary nodes, MCP env tools (200/200 tests)

Completes Sprint 10. Adds EnvironmentSpec AST node, capability validation
(E0501), annotation compatibility checks (E0502-E0505), env-aware lowering
hints, 3 host boundary AST nodes (HostCall, ScheduleTask, ModuleLoad),
and 4 MCP environment tools. 38 MCP tools total.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

editor/tests/step285_test.cpp

@@ -7,6 +7,9 @@
 #include "ast/Function.h"
 #include "ast/Serialization.h"
 #include "EnvironmentSpec.h"
+#include "ASTUtils.h"
+#include "CompactAST.h"
+#include "SidecarPersistence.h"
 #include <nlohmann/json.hpp>
 
 using json = nlohmann::json;