Clarify changed and deleted files in the file viewer (#2670)

* fix(app): distinguish changed and deleted files

Successful reads now reconcile transient missing events without letting stale
cached data mask a deletion. File notices expose only actions valid for the
current buffer state.

* fix(app): preserve file state ordering

* fix(app): allow retrying file checks

* fix(app): clear unchanged file conflicts

* fix(app): keep file conflict recovery consistent

Own disk observation and read ordering in one model so stale reads and failed subscriptions cannot produce contradictory actions.

* fix(app): allow retrying file preview errors

Preserve daemon read errors and expose retry for initial and non-editable file loads.

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

@@ -1502,7 +1502,9 @@ export const en = {
         cursor: "Line {{line}}, column {{column}}",
         preview: "Preview",
         source: "Source",
-        unavailableTitle: "File unavailable on disk",
+        deletedTitle: "File deleted on disk",
+        checkFailedTitle: "Couldn't check file on disk",
+        preservedDescription: "The open copy is preserved.",
         conflictDescription: "The local buffer was preserved. Choose which version to keep.",
         overwrite: "Overwrite",
         reload: "Reload",