Fix isolated SwiftData storage and legacy migration

[ZOB2077]

Summary

• move production SwiftData storage from the shared Application Support/default.store path into Application Support/com.gridnote.app/Gridnote.store
• migrate compatible v1.0.0 stores through a read-only SQLite snapshot with schema and integrity validation
• force XCTest host launches to use in-memory persistence
• bump the application to v1.0.1 (build 11) and document the upgrade

Root cause

Unsandboxed SwiftData apps can resolve the default store to the same user-level Application Support/default.store. Gridnote and icloudmailagent opened that shared path with incompatible models, allowing the Gridnote schema to be replaced.

Validation

• all GridnoteTests unit tests pass
• Release build succeeds with Xcode 27 beta
• repository hygiene check passes
• DMG verifies successfully
• ZIP contains Gridnote 1.0.1 with a valid ad-hoc signature

UI automation was intentionally skipped because it triggers macOS permission prompts and is not required for this persistence-only change.