refactor(FN-2134): remove legacy memory path exports and bootstrap aliases

- Remove legacy memory path constants/helpers from core exports and backend contract surface
- Simplify memory bootstrap to initialize canonical layered memory files without seeding from .fusion/memory.md
- Update core memory tests to assert canonical .fusion/memory/MEMORY.md behavior and legacy-path rejection
- Refresh dashboard and docs naming/references to reflect canonical long-term memory path semantics

packages/core/src/store.ts

@@ -16,7 +16,7 @@ import { InsightStore } from "./insight-store.js";
 import { BackwardCompat, ProjectRequiredError } from "./migration.js";
 import { CentralCore } from "./central-core.js";
 import { getTaskMergeBlocker } from "./task-merge.js";
-import { ensureMemoryFile, ensureMemoryFileWithBackend } from "./project-memory.js";
+import { ensureMemoryFileWithBackend } from "./project-memory.js";
 import { runCommandAsync } from "./run-command.js";
 
 /**