Fix Store updater status and stale chat reload races

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Bug and impact

• Microsoft Store installs reported canceled or failed update operations as successful and told users a restart may be required even when no update was installed.
• A recent post-send SQLite reload could overwrite the UI with the sender thread after the user switched conversations, making the selected thread display the wrong transcript.

Root cause

• install_store_updates ignored StorePackageUpdateResult.OverallState and always returned restartRequired: true once the Store async operation completed.
• loadActiveThread only guarded async responses with a sequence id; post-send/recipe reloads did not verify the source conversation was still active.

Fix

• Treat only StorePackageUpdateState::Completed as a successful Store install, return non-restarting success for Canceled, and surface all other states as errors.
• Keep the active conversation ref synchronized with selection changes, require async thread loads to match both sequence and active conversation, and skip post-send/recipe reloads when the user has moved to another thread.

Validation

• npm ci && npm run build
• cargo check --manifest-path src-tauri/Cargo.toml
• cargo check --manifest-path src-tauri/Cargo.toml --target x86_64-pc-windows-gnu