test: Achieve 100% coverage on Memory and InMemoryStorage

- Add comprehensive unit tests for InMemoryStorage (91 tests)
- Add comprehensive unit tests for Memory class (62 tests)
- Cover all edge cases including working memory hydration and tokenCount:0
- Add @vitest/coverage-v8 dependency for coverage reporting
- Total: 153 passing tests with 100% coverage on core memory classes

Coverage results:
- memory.ts: 100% statements, 100% branch, 100% functions
- in-memory.ts: 100% statements, 100% branch, 100% functions

Author: mattapperson

.speakeasy/gen.yaml

@@ -37,6 +37,7 @@ typescript:
       '@types/node': ^22.13.12
       dotenv: ^16.4.7
       vitest: ^3.2.4
+      '@vitest/coverage-v8': ^3.2.4
     peerDependencies: {}
   additionalPackageJSON: {}
   author: OpenRouter