fix(app): open Changes on the populated comparison (#3636)

* fix(app): restore smart Changes comparison selection

The tab migration persisted the selected comparison, pinning Changes to an empty view after checkout state changed. Keep comparison overrides ephemeral per surface and expire them when dirtiness changes, while preserving only presentation state in tabs.

* chore(app): date Changes compatibility cleanup

packages/app/src/i18n/resources/en.ts

@@ -883,6 +883,8 @@ export const en = {
         failedRefresh: "Failed to refresh git state.",
         emptyHiddenWhitespace: "No visible changes after hiding whitespace",
         emptyUncommitted: "No uncommitted changes",
+        seeUncommittedChanges: "See uncommitted changes",
+        seeCommittedChanges: "See committed changes",
         emptyAgainstBase: "No changes vs {{baseRef}}",
         checkingRepository: "Checking repository...",
         notRepository: "Not a git repository",