ci: bisect the diagnostic workflow

Co-authored-by: arena-agent <297053741+arena-agent@users.noreply.github.com>

Author: hyperpolymath

.github/workflows/zz-probe-a.yml

@@ -0,0 +1,25 @@
+name: ZZ probe a
+
+on:
+  push:
+    branches: [arena/5b8efe75-echidna]
+
+permissions:
+  contents: read
+
+jobs:
+  diag:
+    timeout-minutes: 25
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v7.0.1
+
+      - name: Install Rust toolchain
+        uses: dtolnay/rust-toolchain@v1
+        with:
+          toolchain: stable
+          components: clippy, rustfmt
+
+      - name: Say hi
+        run: echo hi

.github/workflows/zz-probe-b.yml

@@ -0,0 +1,42 @@
+name: ZZ probe b
+
+on:
+  push:
+    branches: [arena/5b8efe75-echidna]
+
+permissions:
+  contents: read
+  pull-requests: write
+
+jobs:
+  diag:
+    timeout-minutes: 25
+    runs-on: ubuntu-latest
+    env:
+      GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+    steps:
+      - name: Install native schema compilers
+        run: |
+          sudo apt-get update
+          sudo apt-get install -y capnproto protobuf-compiler pkg-config libssl-dev
+
+      - name: Run the gates
+        run: |
+          set +e
+          {
+            echo '=== cargo fmt ==='
+            cargo fmt --all -- --check 2>&1 | head -n 150
+          } > /tmp/diag.txt
+          cat /tmp/diag.txt
+
+      - name: Comment the diagnostics
+        if: always()
+        run: |
+          {
+            echo '### Diagnostics (temporary)'
+            echo
+            echo '```'
+            head -c 50000 /tmp/diag.txt
+            echo
+            echo '```'
+          } > /tmp/body.md