refactor(core): finish test layer node conversion

[jlongster]

Summary

• Add node exports for individual tool registration layers and MoveSession so tests can build service graphs through LayerNode/AppNodeBuilder
• Convert the remaining core service test environments from manual defaultLayer/layer composition to node graphs and replacement tuples
• Leave only platform/test-infrastructure layers in core test matches, such as TestConsole, ConfigProvider, SqliteClient, Logger, and recorded LLM transport layers

Testing

• bun typecheck in packages/core
• bun test test/file-mutation.test.ts test/tool-write.test.ts test/tool-edit.test.ts test/tool-apply-patch.test.ts test/tool-bash.test.ts test/tool-read.test.ts test/tool-skill.test.ts test/permission.test.ts test/move-session.test.ts
• bun test test/instruction-context.test.ts test/location-layer.test.ts test/filesystem/watcher.test.ts test/event.test.ts test/snapshot.test.ts test/config/config.test.ts test/plugin/provider-dynamic.test.ts test/config/plugin.test.ts
• bun test test/filesystem/watcher.test.ts
• bun test test/session-runner.test.ts test/session-runner-recorded.test.ts
• bun test test/database-migration.test.ts test/util/effect-flock.test.ts
• bun turbo typecheck (pre-push hook)