[ci] split toranj unit test and build checks into separate jobs (#13597)

Previously, the `toranj-unittest` workflow job serially executed unit
tests alongside various build configuration checks (including log
levels, radio link combinations, and feature flags), leading to longer
job runtimes.

This commit splits this work into independent, parallel jobs:
- `toranj-unittest`: Builds simulation mode and runs `ninja test`.
- `toranj-build-log-level`: Validates builds across all log levels
  (DEBG, INFO, NOTE, WARN, CRIT, NONE).
- `toranj-build-ncp`: Validates NCP builds across radio links (15.4,
  trel, 15.4+trel).
- `toranj-build-posix`: Validates POSIX builds across radio links (15.4,
  trel, 15.4+trel).
- `toranj-build`: Validates feature builds in parallel (platform key
  reference, CSL debug).

Additionally, this removes the redundant `actions/setup-python` step
from these jobs as they only require CMake and Ninja, and cleans up
unused `PR_BODY` environment variables.

.github/workflows/toranj.yml

@@ -73,8 +73,6 @@ jobs:
         cache: pip
     - name: Bootstrap
       timeout-minutes: 10
-      env:
-        PR_BODY: "${{ github.event.pull_request.body }}"
       run: |
         sudo apt-get update
         sudo apt-get --no-install-recommends install -y ninja-build lcov
@@ -110,8 +108,6 @@ jobs:
         cache: pip
     - name: Bootstrap
       timeout-minutes: 10
-      env:
-        PR_BODY: "${{ github.event.pull_request.body }}"
       run: |
         sudo apt-get update
         sudo apt-get --no-install-recommends install -y ninja-build lcov
@@ -143,14 +139,8 @@ jobs:
       with:
         submodules: recursive
         persist-credentials: false
-    - uses: actions/setup-python@5fda3b95a4ea91299a34e894583c3862153e4b97 # v7.0.0
-      with:
-        python-version: '3.12'
-        cache: pip
     - name: Bootstrap
       timeout-minutes: 10
-      env:
-        PR_BODY: "${{ github.event.pull_request.body }}"
       run: |
         sudo apt-get update
         sudo apt-get --no-install-recommends install -y ninja-build
@@ -158,40 +148,112 @@ jobs:
       run: |
         ./tests/toranj/build.sh all
         ninja test
-        #- - - - - - - - - - - - - - - - - - - - - - - - - - -
-        # Validate posix builds with different radio configs
-        git clean -dfx
-        ./tests/toranj/build.sh ncp-15.4
-        git clean -dfx
-        ./tests/toranj/build.sh ncp-trel
-        git clean -dfx
-        ./tests/toranj/build.sh ncp-15.4+trel
-        git clean -dfx
-        ./tests/toranj/build.sh posix-15.4
-        git clean -dfx
-        ./tests/toranj/build.sh posix-15.4+trel
-        git clean -dfx
-        ./tests/toranj/build.sh posix-trel
-        #- - - - - - - - - - - - - - - - - - - - - - - - - - -
-        # Log levels
-        git clean -dfx
-        ./tests/toranj/build.sh --log-level DEBG all
-        git clean -dfx
-        ./tests/toranj/build.sh --log-level INFO all
-        git clean -dfx
-        ./tests/toranj/build.sh --log-level NOTE all
-        git clean -dfx
-        ./tests/toranj/build.sh --log-level WARN all
-        git clean -dfx
-        ./tests/toranj/build.sh --log-level CRIT all
-        git clean -dfx
-        ./tests/toranj/build.sh --log-level NONE all
-        #- - - - - - - - - - - - - - - - - - - - - - - - - - -
-        git clean -dfx
-        ./tests/toranj/build.sh --enable-plat-key-ref all
-        #- - - - - - - - - - - - - - - - - - - - - - - - - - -
-        git clean -dfx
-        ./tests/toranj/build.sh --enable-csl-debug --log-level DEBG all
+
+  toranj-build-log-level:
+    name: toranj-build-log-level-${{ matrix.LOG_LEVEL }}
+    runs-on: ubuntu-24.04
+    strategy:
+      fail-fast: false
+      matrix:
+        LOG_LEVEL: ['DEBG', 'INFO', 'NOTE', 'WARN', 'CRIT', 'NONE']
+    steps:
+    - name: Harden Runner
+      uses: step-security/harden-runner@bf7454d06d71f1098171f2acdf0cd4708d7b5920 # v2.20.0
+      with:
+        egress-policy: audit # TODO: change to 'egress-policy: block' after couple of runs
+
+    - uses: actions/checkout@08c6903cd8c0fde910a37f88322edcfb5dd907a8 # v5.0.0
+      with:
+        submodules: recursive
+        persist-credentials: false
+    - name: Bootstrap
+      timeout-minutes: 10
+      run: |
+        sudo apt-get update
+        sudo apt-get --no-install-recommends install -y ninja-build
+    - name: Build
+      run: |
+        ./tests/toranj/build.sh --log-level ${{ matrix.LOG_LEVEL }} all
+
+  toranj-build-ncp:
+    name: toranj-build-ncp-${{ matrix.RADIO_LINK }}
+    runs-on: ubuntu-24.04
+    strategy:
+      fail-fast: false
+      matrix:
+        RADIO_LINK: ['15.4', 'trel', '15.4+trel']
+    steps:
+    - name: Harden Runner
+      uses: step-security/harden-runner@bf7454d06d71f1098171f2acdf0cd4708d7b5920 # v2.20.0
+      with:
+        egress-policy: audit # TODO: change to 'egress-policy: block' after couple of runs
+
+    - uses: actions/checkout@08c6903cd8c0fde910a37f88322edcfb5dd907a8 # v5.0.0
+      with:
+        submodules: recursive
+        persist-credentials: false
+    - name: Bootstrap
+      timeout-minutes: 10
+      run: |
+        sudo apt-get update
+        sudo apt-get --no-install-recommends install -y ninja-build
+    - name: Build
+      run: |
+        ./tests/toranj/build.sh ncp-${{ matrix.RADIO_LINK }}
+
+  toranj-build-posix:
+    name: toranj-build-posix-${{ matrix.RADIO_LINK }}
+    runs-on: ubuntu-24.04
+    strategy:
+      fail-fast: false
+      matrix:
+        RADIO_LINK: ['15.4', 'trel', '15.4+trel']
+    steps:
+    - name: Harden Runner
+      uses: step-security/harden-runner@bf7454d06d71f1098171f2acdf0cd4708d7b5920 # v2.20.0
+      with:
+        egress-policy: audit # TODO: change to 'egress-policy: block' after couple of runs
+
+    - uses: actions/checkout@08c6903cd8c0fde910a37f88322edcfb5dd907a8 # v5.0.0
+      with:
+        submodules: recursive
+        persist-credentials: false
+    - name: Bootstrap
+      timeout-minutes: 10
+      run: |
+        sudo apt-get update
+        sudo apt-get --no-install-recommends install -y ninja-build
+    - name: Build
+      run: |
+        ./tests/toranj/build.sh posix-${{ matrix.RADIO_LINK }}
+
+  toranj-build-feature:
+    name: toranj-build-feature-(${{ matrix.OPTIONS }})
+    runs-on: ubuntu-24.04
+    strategy:
+      fail-fast: false
+      matrix:
+        OPTIONS:
+          - '--enable-plat-key-ref all'
+          - '--enable-csl-debug --log-level DEBG all'
+    steps:
+    - name: Harden Runner
+      uses: step-security/harden-runner@bf7454d06d71f1098171f2acdf0cd4708d7b5920 # v2.20.0
+      with:
+        egress-policy: audit # TODO: change to 'egress-policy: block' after couple of runs
+
+    - uses: actions/checkout@08c6903cd8c0fde910a37f88322edcfb5dd907a8 # v5.0.0
+      with:
+        submodules: recursive
+        persist-credentials: false
+    - name: Bootstrap
+      timeout-minutes: 10
+      run: |
+        sudo apt-get update
+        sudo apt-get --no-install-recommends install -y ninja-build
+    - name: Build
+      run: |
+        ./tests/toranj/build.sh ${{ matrix.OPTIONS }}
 
   toranj-macos:
     name: toranj-macos
@@ -208,12 +270,10 @@ jobs:
         persist-credentials: false
     - name: Bootstrap
       timeout-minutes: 10
-      env:
-        PR_BODY: "${{ github.event.pull_request.body }}"
       run: |
         brew update
         brew install ninja
-    - name: Build & Run
+    - name: Build
       run: |
         ./tests/toranj/build.sh posix-15.4