ci: move off the Node 20 runtime

GitHub is deprecating Node 20 and has begun forcing these actions onto Node 24
regardless, so they are already running on a runtime they do not declare.

Two actions were responsible. actions/checkout declares node20 and appears on
six steps that expand to ten job runs through the two matrices -- which is
exactly the ten warnings the last run reported. actions/deploy-pages declares
node20 on the one job that publishes. Both move to the major that adopted Node
24.

actions/upload-pages-artifact stays at v3 on purpose, and the reason is written
beside it so the next person does not finish the job. It is a composite action
with no Node runtime of its own, so it was never part of this deprecation, and
v3 alongside deploy-pages@v5 is the pairing GitHub ships in its own Pages
starter workflow. Newer majors exist; swapping a tested pairing for an untested
one to fix a problem it does not have is not an improvement.

checkout stops at v5 rather than v7 for the same reason. v6 moves credentials to
a separate file and v7 blocks fork-PR checkout for pull_request_target and
workflow_run -- neither of which this workflow uses, so v7 would be safe. v5 is
the version that fixes Node 20, and a CI file is a poor place for changes that
buy nothing.

Verified as far as it can be locally: the workflow still parses and still has
seven jobs, both target majors exist, and the runtime each action declares was
read from its own action.yml rather than assumed. Whether the actions themselves
behave is what the next run answers, and a failure would be confined to
publish-docs.

Author: Onwcan

.github/workflows/ci.yml

@@ -33,7 +33,7 @@ jobs:
             cc: clang-18
             cxx: clang++-18
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v5
 
       - name: Install toolchain
         run: |
@@ -60,7 +60,7 @@ jobs:
       matrix:
         preset: [asan, tsan]
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v5
       - name: Install toolchain
         run: sudo apt-get update && sudo apt-get install -y ninja-build clang-18
       - name: Configure
@@ -82,7 +82,7 @@ jobs:
     name: benchmarks build and run
     runs-on: ubuntu-24.04
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v5
       - name: Install toolchain
         run: sudo apt-get update && sudo apt-get install -y ninja-build
 
@@ -107,7 +107,7 @@ jobs:
     name: clang-tidy + clang-format
     runs-on: ubuntu-24.04
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v5
       - name: Install toolchain
         run: sudo apt-get update && sudo apt-get install -y ninja-build clang-18 clang-tidy-18 clang-format-18
 
@@ -135,7 +135,7 @@ jobs:
     name: installed package is consumable
     runs-on: ubuntu-24.04
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v5
       - name: Install toolchain
         run: sudo apt-get update && sudo apt-get install -y ninja-build
 
@@ -332,7 +332,7 @@ jobs:
     name: API reference builds clean
     runs-on: ubuntu-24.04
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v5
       - name: Install toolchain
         run: sudo apt-get update && sudo apt-get install -y ninja-build doxygen
 
@@ -348,6 +348,10 @@ jobs:
           cmake --build build --target docs
 
       - name: Upload for publication
+        # Deliberately still v3. It is a composite action with no Node runtime
+        # of its own, so it is not part of the Node 20 deprecation, and v3 with
+        # deploy-pages@v5 is the pairing GitHub ships in its own Pages starter
+        # workflow. Newer majors exist; none of them buy anything here.
         uses: actions/upload-pages-artifact@v3
         with:
           path: build/docs/html
@@ -373,4 +377,4 @@ jobs:
     steps:
       - name: Deploy to GitHub Pages
         id: deployment
-        uses: actions/deploy-pages@v4
+        uses: actions/deploy-pages@v5