infra(kapsule): downgrade CI pool to GP1-M — GP1-L hits vCPU quota

GP1-L (32 vCPU) creation_error due to project vCPU quota limits.
GP1-M (16 vCPU, 64GB) is 2x the previous GP1-S and within quota.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

infra/live/production/kapsule/terragrunt.hcl

@@ -27,6 +27,6 @@ inputs = {
 
   # CI build pool (ephemeral runner pods, scale-to-zero)
   enable_ci_build_pool = true
-  ci_build_type        = "GP1-L"
+  ci_build_type        = "GP1-M"
   ci_build_max_size    = 2
 }