Document echovault memory workflow in CLAUDE.md

Load memory_context at session start, search before topic work,
save decisions/bugs/gotchas before ending a session.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

CLAUDE.md

@@ -61,3 +61,13 @@ dotnet run --project samples/MrGameEng.Sample
 - Nullable reference types enabled, warnings as errors, file-scoped namespaces.
 - Public engine API requires XML doc comments (English).
 - Tests: xUnit, named `Method_Scenario_Expectation`.
+
+## Memory (echovault MCP)
+
+- At session start, call `memory_context` to load prior decisions for this project;
+  call `memory_search` before working on a topic that may have prior context
+  (e.g. "renderer", "transitions", "generator").
+- Before ending a session where you decided, fixed or learned something, save it with
+  `memory_save`: decisions (X over Y + why), bug root causes, non-obvious gotchas
+  (e.g. Friflo/Myra API traps). Write for a future agent with zero context.
+- Don't save what the repo already records (code, docs/, git history) or trivia.