fix(webapp): stop slow database cleanup on project deletion (#4191)

## Summary

Deleting a project triggered an unbounded database cleanup that scanned
the project's entire run history, so deleting a project with many runs
could be very slow. Project deletion is a soft delete again: run data is
retained and the deletion completes quickly.

## Fix

Project deletion ran a cascade hard-delete whose `BulkActionItem` step
filtered through a relation to `TaskRun` scoped by `projectId`. Prisma
compiles that to an `EXISTS`-join over the project's entire `TaskRun`
set (a large, hot table with no `projectId` index), and it ran on every
project deletion unconditionally.

Removing the cascade-cleanup call restores the prior soft-delete
behaviour: queues are removed, the project is marked deleted, and run
data is retained. The cascade-cleanup service (added in
[#4117](#4117)) had no
other callers, so it and its test are deleted.

Author: d-cs

.server-changes/fix-slow-project-deletion.md

@@ -0,0 +1,6 @@
+---
+area: webapp
+type: fix
+---
+
+Deleting a project no longer triggers a slow database cleanup that could hang on projects with many runs.

apps/webapp/app/services/archiveBranch.server.ts

@@ -82,8 +82,8 @@ export class ArchiveBranchService {
       }
 
       // Branch archive is a SOFT update — do NOT hard-delete run-ops rows here (it would destroy a
-      // retained branch's history). RunOpsCascadeCleanupService.cleanupEnvironment belongs on the
-      // env hard-delete/purge path (owned by the cloud env-purge runbook), which has no site today.
+      // retained branch's history). Any env hard-delete/purge belongs on a dedicated purge path
+      // (owned by the cloud env-purge runbook), which has no site today.
       const slug = `${environment.slug}-${nanoid(6)}`;
       const shortcode = slug;
 

apps/webapp/app/services/deleteProject.server.ts

@@ -3,7 +3,6 @@ import { prisma } from "~/db.server";
 import { marqs } from "~/v3/marqs/index.server";
 import { engine } from "~/v3/runEngine.server";
 import { controlPlaneResolver } from "~/v3/runOpsMigration/controlPlaneResolver.server";
-import { RunOpsCascadeCleanupService } from "~/v3/runOpsMigration/runOpsCascadeCleanup.server";
 
 type Options = ({ projectId: string } | { projectSlug: string }) & {
   userId: string;
@@ -51,9 +50,7 @@ export class DeleteProjectService {
       });
     }
 
-    // Hard-delete the project's run-ops rows across both run-ops DBs (replaces the cloud-only
-    // dropped cross-seam FK cascades). Idempotent; uses the run-ops writers, not #prismaClient.
-    await new RunOpsCascadeCleanupService().cleanupProject(project.id);
+    // Soft delete only: run-ops rows are intentionally retained (no hard-delete cascade here).
 
     // Mark the project as deleted (do this last because it makes it impossible to try again)
     // - This disables all API keys