fix(db): re-root a rescued folder whose parent is soft-deleted

Step 1's parent resolver checked existence and workspace but not reachability,
so an ACTIVE stranded folder whose parent is soft-deleted kept that parent and
landed in Recently Deleted — the same invisibility the re-root fallback exists
to prevent, and the opposite of resolveRestoredFolderId, which re-roots a
restored folder whose original parent is archived.

A soft-deleted row is exempt: it may keep a soft-deleted parent, since that is
the normal shape of an archived subtree and flattening it would destroy the
hierarchy a later restore rebuilds.

Verified differentially against Postgres 17.9: pre-fix both active rows keep the
deleted parent, post-fix both re-root while the archived child keeps its parent.

Author: waleedlatif1

packages/db/migrations/0275_drop_legacy_folder_tables.sql

@@ -53,9 +53,18 @@ BEGIN
 		FROM "workflow_folder" l
 		WHERE NOT EXISTS (SELECT 1 FROM "folder" f WHERE f.id = l.id)
 	),
-	-- A parent is only usable if it will exist AND shares this row's workspace — the
-	-- `folder_parent_resource_type_match` trigger enforces the workspace match, and the legacy
-	-- self-FK never did, so a cross-workspace parent is representable in the source data.
+	-- A parent is only usable if it will exist, shares this row's workspace, and leaves the row
+	-- REACHABLE. The workspace match is enforced by the `folder_parent_resource_type_match`
+	-- trigger and was never enforced by the legacy self-FK, so a cross-workspace parent is
+	-- representable in the source data. Reachability is the subtler half: filing an ACTIVE
+	-- folder under a soft-deleted parent hides it in Recently Deleted just as thoroughly as a
+	-- dangling parent would, so it re-roots too — matching `resolveRestoredFolderId`, which
+	-- re-roots a restored folder whose original parent is archived.
+	--
+	-- A soft-deleted row is exempt: it MAY keep a soft-deleted parent, because that is the
+	-- normal shape of an archived subtree and flattening it would destroy the hierarchy a
+	-- later restore rebuilds.
+	--
 	-- Anything else re-roots to the workspace root: losing one level of nesting beats losing the
 	-- folder and stranding every workflow inside it.
 	resolved AS (
@@ -65,9 +74,12 @@ BEGIN
 				WHEN EXISTS (
 					SELECT 1 FROM "folder" f
 					WHERE f.id = s.parent_id AND f.resource_type = 'workflow' AND f.workspace_id = s.workspace_id
+						AND (s.deleted_at IS NOT NULL OR f.deleted_at IS NULL)
 				) THEN s.parent_id
 				WHEN EXISTS (
-					SELECT 1 FROM stranded s2 WHERE s2.id = s.parent_id AND s2.workspace_id = s.workspace_id
+					SELECT 1 FROM stranded s2
+					WHERE s2.id = s.parent_id AND s2.workspace_id = s.workspace_id
+						AND (s.deleted_at IS NOT NULL OR s2.deleted_at IS NULL)
 				) THEN s.parent_id
 				ELSE NULL
 			END AS resolved_parent
@@ -152,16 +164,20 @@ BEGIN
 		FROM "workspace_file_folders" l
 		WHERE NOT EXISTS (SELECT 1 FROM "folder" f WHERE f.id = l.id)
 	),
+	-- Same reachability rule as the workflow tree above.
 	resolved AS (
 		SELECT s.*,
 			CASE
 				WHEN s.parent_id IS NULL THEN NULL
 				WHEN EXISTS (
 					SELECT 1 FROM "folder" f
 					WHERE f.id = s.parent_id AND f.resource_type = 'file' AND f.workspace_id = s.workspace_id
+						AND (s.deleted_at IS NOT NULL OR f.deleted_at IS NULL)
 				) THEN s.parent_id
 				WHEN EXISTS (
-					SELECT 1 FROM stranded s2 WHERE s2.id = s.parent_id AND s2.workspace_id = s.workspace_id
+					SELECT 1 FROM stranded s2
+					WHERE s2.id = s.parent_id AND s2.workspace_id = s.workspace_id
+						AND (s.deleted_at IS NOT NULL OR s2.deleted_at IS NULL)
 				) THEN s.parent_id
 				ELSE NULL
 			END AS resolved_parent