ci: give the reusable test workflows distinct concurrency groups

When on_tag.yml calls build_test and build_test_mobile as reusable workflows,
github.workflow resolves to the caller ("on_tag") for both, so their identical
'${{ github.workflow }}-${{ github.ref }}' concurrency group collided and
cancel-in-progress cancelled one of them (build_test_mobile), which then blocked
the gated release jobs. Hardcode a per-workflow literal in the group so it stays
distinct whether the workflow runs standalone (PR/push) or reused (tag).

Author: vackva

.github/workflows/build_test.yml

@@ -15,8 +15,12 @@ env:
   SCCACHE_GHA_ENABLED: "true"
 
 # When pushing new commits, cancel any workflows with the same name on that branch
+# Hardcode the workflow name (not ${{ github.workflow }}): when on_tag.yml calls this
+# as a reusable workflow, github.workflow becomes "on_tag" — shared with the other
+# reusable test workflow, so cancel-in-progress would cancel one of them. A literal
+# keeps the group distinct in both the standalone (PR/push) and reused (tag) cases.
 concurrency:
-  group: ${{ github.workflow }}-${{ github.ref }}
+  group: build_test-${{ github.ref }}
   cancel-in-progress: true
 
 jobs:

.github/workflows/build_test_mobile.yml

@@ -27,8 +27,12 @@ on:
 env:
   SCCACHE_GHA_ENABLED: "true"
 
+# Hardcode the workflow name (not ${{ github.workflow }}): when on_tag.yml calls this
+# as a reusable workflow, github.workflow becomes "on_tag" — shared with build_test,
+# so cancel-in-progress would cancel one of them. A literal keeps the group distinct
+# in both the standalone (PR/push) and reused (tag) cases.
 concurrency:
-  group: ${{ github.workflow }}-${{ github.ref }}
+  group: build_test_mobile-${{ github.ref }}
   cancel-in-progress: true
 
 jobs: