sibling explicit-grouping implementation: commit all work, removal of stray scratch files; update docs and status; keep P1 fix and other senior details

db/migrations/20261014120001_import_grouping_decisions.php

@@ -0,0 +1,26 @@
+<?php
+
+declare(strict_types=1);
+
+use Phinx\Migration\AbstractMigration;
+
+final class ImportGroupingDecisions extends AbstractMigration
+{
+    public function up(): void
+    {
+        $this->table('import_jobs_decisions', ['id' => false, 'primary_key' => ['job_id', 'source_path']])
+            ->addColumn('job_id', 'integer', ['signed' => false])
+            ->addColumn('source_path', 'text')
+            ->addColumn('model_id', 'integer', ['signed' => false])
+            ->addColumn('context', 'jsonb', ['default' => '{}'])
+            ->addColumn('created_at', 'timestamp', ['default' => 'CURRENT_TIMESTAMP'])
+            ->addForeignKey('job_id', 'import_jobs', 'id', ['delete' => 'CASCADE', 'update' => 'NO_ACTION'])
+            ->addIndex(['model_id'], ['name' => 'idx_import_decisions_model'])
+            ->create();
+    }
+
+    public function down(): void
+    {
+        $this->table('import_jobs_decisions')->drop()->save();
+    }
+}