fix: use per-host deploy concurrency groups to prevent cancellation

Move concurrency from workflow-level to job-level with per-host groups.
Workflow-level concurrency only allows one pending run, canceling earlier
queued runs when a new one arrives. Per-host groups let each host queue
independently.

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

Author: stackptr

.github/workflows/deploy.yml

@@ -7,15 +7,14 @@ on:
     branches: [main]
   workflow_dispatch:
 
-concurrency:
-  group: deploy
-  cancel-in-progress: false
-
 jobs:
   deploy:
     if: >-
       github.event_name == 'workflow_dispatch' ||
       github.event.workflow_run.conclusion == 'success'
+    concurrency:
+      group: deploy-${{ matrix.host }}
+      cancel-in-progress: false
     strategy:
       matrix:
         include: