Investigate prebuild create vs claim build times in dogfood

## Description

In our dogfood environment, the “Write Coder on Coder” template has prebuilds enabled for certain presets. We recently introduced new metrics for prebuild creation time (building into the pool) and prebuild claim time https://github.com/coder/coder/pull/19503, and added them to our observability stack.

These metrics show that claim durations sometimes exceed creation by about 1–2 seconds. Because prebuilds maintain a ready-to-use pool to reduce workspace start time, claims should be consistently faster than creations.

We already use a Terraform `lifecycle` block with `ignore_changes` as recommended in the [docs](https://coder.com/docs/admin/templates/extending-templates/prebuilt-workspaces#preventing-resource-replacement), yet this pattern suggests Terraform may still be replacing or re-provisioning resources during claim, or the claim path is performing extra work.

For reference, see the attached screenshot comparing average build times for a prebuild creation versus a claim on the Falkenstein preset in our dogfood instance.

## Investigation scope

Investigate the source of the additional claim-path latency relative to the create path.

Comienza con la creación de prebuilds y las métricas de claim en el stack de observabilidad, comparando los datos de dogfood de Falkenstein y el bloque lifecycle de Terraform con ignore_changes descrito en la documentación enlazada. Sigue las rutas de create y claim para identificar el origen de los 1–2 segundos adicionales; se considera terminado cuando se haya explicado la latencia adicional de claim y se haya confirmado o descartado cualquier reemplazo o reprovisionamiento de Terraform.

Escrito por el modelo de indexación a partir del texto del issue.