feat: compare_schemas command + diff staging into the changes queue (Task 15)

desktop/src/lib/commands.ts

@@ -2,6 +2,7 @@ import { invoke } from "@tauri-apps/api/core";
 import type { Connection, ConnectionInput, ConnectionTestResult, Folder, FolderInput, Tag, TagInput, Settings, ImportResult, TableInfo, QueryResult, BackupOptions, RestoreOptions, SyncOptions, PgToolStatus, MySqlToolStatus, MySqlBackupOptions, MySqlRestoreOptions, SqliteBackupOptions, SqliteRestoreOptions, FunctionInfo, TriggerInfo, SequenceInfo, EnumInfo, ExtensionInfo, SchemaGraph, IndexInfo, ConstraintInfo, RecentConnection, ObjectSearchHit, DependencyInfo, RoleInfo, PrivilegeEntry, RebuildReadiness, MaintenanceResult, TablespaceInfo, ColumnInfo, HypertableListResponse, MultiQueryResult } from "./types";
 import type { FilterRule, SortRule } from "../stores/dbViewerStore";
 import type { ChangePayload } from "./changePayload";
+import type { DiffReport } from "./types";
 import { buildObjectDdl as buildObjectDdlImpl, type ObjectKind, type DdlParams } from "./objectCrud";
 
 export { type ObjectKind, type DdlParams };
@@ -418,4 +419,14 @@ export async function getTablespaces(connectionId: string): Promise<TablespaceIn
 }
 export async function buildRebuildScript<C extends { name: string; type: string; nullable: boolean; default: string | null; is_pk: boolean }[]>(connectionId: string, schema: string, table: string, newColumns: C): Promise<string> {
   return invoke<string>("build_rebuild_script", { connectionId, schema, table, newColumns });
-}
+}
+export async function compareSchemas(
+  sourceConnectionId: string,
+  sourceSchema: string,
+  targetConnectionId: string,
+  targetSchema: string,
+): Promise<DiffReport> {
+  return invoke<DiffReport>("compare_schemas", {
+    sourceConnectionId, sourceSchema, targetConnectionId, targetSchema,
+  });
+}

desktop/src/lib/types.ts

@@ -506,4 +506,25 @@ export interface Relationship {
 export interface SchemaGraph {
   tables: TableNode[];
   relationships: Relationship[];
-}
+}
+export interface DiffDetailLine {
+  label: string;
+  old: string;
+  new: string;
+}
+
+export interface DiffItem {
+  object_type: string;
+  name: string;
+  kind: "added" | "removed" | "changed";
+  detail: DiffDetailLine[];
+  sync_sql: string[];
+  destructive: boolean;
+}
+
+export interface DiffReport {
+  items: DiffItem[];
+  source_label: string;
+  target_label: string;
+  truncated: boolean;
+}