Stack page links deploys/rollbacks to tasks#show, which 500s on @task.definition.id (nil for deploys)

Summary

On a stack's show page, every entry in the Previous Deploys list (including Shipit::Deploy and Shipit::Rollback records) is linked to tasks#show (/stacks/:id/tasks/:task_id). Clicking on a "deploy" or "rollback" task that way raises:

ActionView::Template::Error (undefined method 'id' for nil)
    app/views/shipit/tasks/show.html.erb:2

so clicking any deploy in Previous Deploys returns a 500.

Note that overriding the link and visiting the same record at /stacks/:id/deploys/:id works fine.

Steps to reproduce

1. Open a stack that has previous deploys.
2. Click a deploy (or rollback) in the Previous Deploys list — it links to /stacks/:id/tasks/:task_id.
3. 500: undefined method 'id' for nil at app/views/shipit/tasks/show.html.erb:2.

Root cause

tasks/show.html.erb renders the task title with @task.definition.id:

<%= @task.active? ? "executing" : "executed" %> <%= @task.definition.id %>

definition is a serialized column populated only for generic shipit.yml tasks.
Deploys and rollbacks don't seem to ever have one (Stack#build_deploy doesn't set it).

This view is only meant for generic tasks — deploys/rollbacks have their own deploys/show and deploys/_deploy. The reason they now reach tasks#show is the deploy list in stacks/show.html.erb:

<%= render partial: 'shipit/tasks/task', collection: @tasks %>

This forces every record through shipit/tasks/_task, which links via stack_task_path → tasks#show. Previously the list used polymorphic rendering:

<%= render @tasks %>

which dispatched each record via to_partial_path: Shipit::Deploy → shipit/deploys/_deploy and Shipit::Rollback (to_partial_path overridden to 'deploys/deploy') → the same deploy partial, both linking to deploys#show. Only generic tasks rendered tasks/_task.

The change came in 793e1d5cc22fece0eb644160026042a483dc1f49, which replaced render @tasks with the explicit single-partial form.
That seemed to have suppressed the implicit-render warning but loses the per-type partial dispatch for the STI subclasses.

Still present on main / 0.45.1.

Possible fixes

• Restore polymorphic rendering (render @tasks) for the deploy list in stacks/show.html.erb; or
• Keep explicit rendering but dispatch per type (deploys/_deploy for Deploy/Rollback, tasks/_task for generic tasks); or
• Make tasks/show.html.erb tolerate a nil definition (e.g. fall back to @task.title) so a deploy routed there doesn't crash.

Environment

• shipit-engine 0.45.1 (also reproducible on 0.44.2)
• Rails 8.1.3

Start with app/views/stacks/show.html.erb and compare its rendering of @tasks with the type-specific partials app/views/shipit/tasks/_task and app/views/shipit/deploys/_deploy. Read app/views/shipit/tasks/show.html.erb and reproduce the Previous Deploys navigation; done means deploys and rollbacks no longer reach the generic task view or produce a 500, while generic tasks still work.