Code health: run the linter from the agents branch

.github/workflows/code-health.yml

@@ -1,8 +1,15 @@
 name: C++ Code Health
+# Stub: the linter (devtools/code_health) and its self-tests live on the fork's agents branch.
+# This checks that branch out next to the code and runs it against the code checkout.
 on:
   push:
     branches: [main]
   pull_request:
+  workflow_dispatch:
+    inputs:
+      base-ref:
+        description: Revision to compare with (e.g. origin/main); empty = whole tree
+        required: false
 
 permissions:
   contents: read
@@ -14,22 +21,33 @@ jobs:
       - uses: actions/checkout@v7
         with:
           fetch-depth: 0
+      - uses: actions/checkout@v7
+        with:
+          repository: dayfine/Arduino-Source
+          ref: agents
+          path: .agents-tools
       - uses: actions/setup-python@v6
         with:
           python-version: '3.11'
           cache: pip
-          cache-dependency-path: devtools/code_health/requirements.txt
-      - run: python -m pip install -r devtools/code_health/requirements.txt
+          cache-dependency-path: .agents-tools/devtools/code_health/requirements.txt
+      - run: python -m pip install -r .agents-tools/devtools/code_health/requirements.txt
       - name: Linter self-tests
+        working-directory: .agents-tools
+        env:
+          CODE_HEALTH_REPO: ${{ github.workspace }}
         run: python -m unittest discover -s devtools/code_health/tests -v
       - name: Check changed C++ files
+        working-directory: .agents-tools
         env:
           PR_BASE: ${{ github.event.pull_request.base.sha }}
+          INPUT_BASE: ${{ inputs.base-ref }}
           PUSH_BASE: ${{ github.event.before }}
+          CODE: ${{ github.workspace }}
         shell: bash
         run: |
-          base="${PR_BASE:-$PUSH_BASE}"
+          base="${PR_BASE:-${INPUT_BASE:-$PUSH_BASE}}"
           if [[ -z "$base" || "$base" == 0000000000000000000000000000000000000000 ]]; then
-            base=$(git hash-object -w -t tree --stdin </dev/null)
+            base=$(git -C "$CODE" hash-object -w -t tree --stdin </dev/null)
           fi
-          python -m devtools.code_health --base-ref "$base" --github
+          python -m devtools.code_health --root "$CODE" --base-ref "$base" --github