[ci] Improve nightlies by dropping trigger workflow, fix naming-scheme

.github/workflows/ci.yml

@@ -1,4 +1,4 @@
-name: CI
+name: Test
 
 on:
   push:

.github/workflows/main-failure-report.yml

@@ -6,7 +6,7 @@ name: Main failure report
 
 on:
   workflow_run:
-    workflows: [CI, Wheels]
+    workflows: [Test, Wheels]
     types: [completed]
 
 permissions:

.github/workflows/nightly.yml

@@ -1,23 +1,25 @@
 name: Nightly
 
-# The full test matrix on a schedule; pr-nightly.yml also runs it on
-# PRs labeled test-nightly.
+# The full test matrix on a schedule; applying the test-nightly label
+# runs it on a PR (re-apply the label for a fresh run).
 
 on:
   schedule:
     - cron: '30 2 * * *'
   workflow_dispatch:
-  workflow_call:
+  pull_request:
+    types: [labeled]
 
 permissions:
   contents: read
 
 concurrency:
-  group: nightly-${{ github.workflow }}
+  group: nightly-${{ github.workflow }}-${{ github.event.pull_request.number || github.ref }}
   cancel-in-progress: true
 
 jobs:
   build-test:
+    if: ${{ github.event_name != 'pull_request' || contains(github.event.pull_request.labels.*.name, 'test-nightly') }}
     name: ${{ matrix.os }}/llvm${{ matrix.llvm }}/py${{ matrix.py }}/c++${{ matrix.cxx }}${{ matrix.vg && '/vg' || '' }}${{ matrix.flavor == 'cling' && '/cling' || '' }}
     strategy:
       fail-fast: false

.github/workflows/wheels.yml

@@ -30,10 +30,10 @@ concurrency:
 
 jobs:
   wheels:
-    name: wheels ${{ matrix.label }}
-    # A labeled event re-runs the workflow only for build-wheels itself;
-    # jobs without a needs edge to this one repeat the guard by alias.
-    if: &label-guard ${{ github.event.action != 'labeled' || github.event.label.name == 'build-wheels' }}
+    name: ${{ matrix.label }}
+    # Label events run only when the PR carries build-wheels, whichever
+    # label fired; jobs without a needs edge repeat the guard by alias.
+    if: &label-guard ${{ github.event.action != 'labeled' || contains(github.event.pull_request.labels.*.name, 'build-wheels') }}
     strategy:
       fail-fast: false
       matrix: