fix(ci): rerun release dependency check on label (#10955)

* ci: run check-no-git-dependencies when A-release label is added late

The check-no-git-dependencies job in tests-unit.yml is gated on the
A-release label, but that workflow's pull_request trigger uses the
default activity types (opened, synchronize, reopened). Adding the label
to an existing PR therefore does not re-run it, so the check stays
skipped until the next push.

Add a dedicated workflow that triggers only on the labeled event and
runs the same check, avoiding a full unit-test re-run on every label
change.

* ci: clarify workflow comment about label-triggered runs

* fix(ci): reuse unit workflow for release labels

---------

Co-authored-by: Gustavo Valverde <g.valverde02@gmail.com>

Author: andres-pcg

.github/workflows/tests-unit.yml

@@ -3,6 +3,7 @@ name: Unit Tests
 on:
   pull_request:
     branches: [main]
+    types: [opened, synchronize, reopened, labeled]
   push:
     branches: [main]
   merge_group:
@@ -27,6 +28,7 @@ env:
 
 jobs:
   changes:
+    if: github.event.action != 'labeled' || github.event.label.name == 'A-release'
     runs-on: ubuntu-latest
     timeout-minutes: 5
     outputs:
@@ -97,7 +99,10 @@ jobs:
 
   unit-tests:
     runs-on: ubuntu-latest
-    if: always()
+    if: >-
+      always() &&
+      (github.event.action != 'labeled' ||
+      github.event.label.name == 'A-release')
     needs:
       - changes
       - run-unit-tests