ci: bench workflows queue instead of cancelling each other

.github/workflows/bench-abba.yml

@@ -8,11 +8,10 @@ on:
   issue_comment:
     types: [created]
 
-# One ABBA run per PR; a re-trigger cancels the stale one. (The single self-hosted
-# bench runner serializes across PRs on its own.)
 concurrency:
-  group: bench-abba-${{ github.event.issue.number }}
-  cancel-in-progress: true
+  # See bench-verify.yml. The single self-hosted bench runner serializes across PRs.
+  group: ${{ startsWith(github.event.comment.body, '/bench-abba') && format('bench-abba-{0}', github.event.issue.number) || format('bench-abba-ignore-{0}', github.run_id) }}
+  cancel-in-progress: false
 
 permissions:
   contents: read

.github/workflows/bench-verify.yml

@@ -5,10 +5,14 @@ on:
   issue_comment:
     types: [created]
 
-# One verifier run per PR; a re-trigger cancels the stale one.
 concurrency:
-  group: bench-verify-${{ github.event.issue.number }}
-  cancel-in-progress: true
+  # Serialization is provided by the single self-hosted bench runner (jobs queue
+  # for it). Never cancel a running bench: real /bench-verify comments share the
+  # per-PR group and queue; any other comment (this workflow fires on every
+  # issue_comment) gets a unique throwaway group so it can't sit in — or evict —
+  # the real queue.
+  group: ${{ startsWith(github.event.comment.body, '/bench-verify') && format('bench-verify-{0}', github.event.issue.number) || format('bench-verify-ignore-{0}', github.run_id) }}
+  cancel-in-progress: false
 
 permissions:
   contents: read

.github/workflows/bench-vs-nightly.yml

@@ -10,8 +10,9 @@ permissions:
   contents: read
 
 concurrency:
+  # Never cancel an in-flight nightly bench; the single bench runner serializes.
   group: bench-vs-nightly-${{ github.ref }}
-  cancel-in-progress: true
+  cancel-in-progress: false
 
 jobs:
   bench-vs:

.github/workflows/benchmark-pr.yml

@@ -27,8 +27,9 @@ permissions:
   actions: read
 
 concurrency:
+  # Runner serializes; never cancel a running bench (group is already unique per run for comment/push events).
   group: benchmark-${{ github.head_ref || github.run_id }}
-  cancel-in-progress: true
+  cancel-in-progress: false
 
 env:
   # Headline program: the ethrex guest ELF proven against a 20-transfer block

.github/workflows/profile-recursion.yml

@@ -15,8 +15,9 @@ permissions:
   pull-requests: write
 
 concurrency:
-  group: profile-recursion-${{ github.event.issue.number || github.run_id }}
-  cancel-in-progress: true
+  # See bench-verify.yml. workflow_dispatch (no comment) falls to the unique run_id group.
+  group: ${{ startsWith(github.event.comment.body, '/profile_recursion') && format('profile-recursion-{0}', github.event.issue.number) || format('profile-recursion-{0}', github.run_id) }}
+  cancel-in-progress: false
 
 jobs:
   # One job per configuration; they run in parallel and each uploads a Markdown