feat(import): say which fields differ, and stop offering to apply nothing

A row marked "edited" or "conflict" gave no way to tell what actually
differs, so a resource that drifted from the file — however it drifted —
reads as an unexplained accusation. The plan now carries the field names
the source and the local copy disagree on, and the row's tooltip lists
them.

The preview's primary button also read "Apply" when the current selection
would change nothing. It now reads "Done", since committing an empty
selection only records the decisions made in the preview.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

crates/yaak-models/bindings/gen_util.ts

@@ -77,6 +77,10 @@ export type ImportPlanItem = {
   selected: boolean;
   resolution?: ImportConflictResolution;
   reason?: ImportPlanReason;
+  /**
+   * Fields where the source and the local copy disagree, so the preview can say why
+   */
+  changedFields: Array<string>;
 };
 
 /**

crates/yaak-models/src/util.rs

@@ -205,6 +205,9 @@ pub struct ImportPlanItem {
     pub resolution: Option<ImportConflictResolution>,
     #[ts(optional)]
     pub reason: Option<ImportPlanReason>,
+    /// Fields where the source and the local copy disagree, so the preview can say why
+    #[serde(default)]
+    pub changed_fields: Vec<String>,
 }
 
 #[derive(Debug, Deserialize, Serialize, TS)]