ci-test: add empty markdown to trigger gate failure

Adds .gitea/workflows/minimum-pr-gate.yml which enforces a lightweight
check on every pull request: Python syntax on changed files, secret scan,
and markdown sanity. Also documents the gate in README.

Closes #521

.gitea/workflows/minimum-pr-gate.yml

@@ -0,0 +1,84 @@
+name: Minimum PR Gate
+
+on:
+  pull_request:
+    branches: [main]
+  workflow_dispatch:
+
+jobs:
+  minimum-pr-gate:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+
+      - name: Determine changed files
+        id: changes
+        run: |
+          if [ "${{ github.event_name }}" = "pull_request" ]; then
+            CHANGED=$(git diff --name-only ${{ github.event.pull_request.base.sha }} ${{ github.event.pull_request.head.sha }})
+          else
+            CHANGED=$(git ls-files)
+          fi
+          echo "changed=${CHANGED}" >> $GITHUB_OUTPUT
+          echo "Changed files:"
+          echo "$CHANGED"
+
+      - name: Python syntax check
+        if: steps.changes.outputs.changed != ''
+        run: |
+          CHANGED_FILES="${{ steps.changes.outputs.changed }}"
+          PY_FILES=$(echo "$CHANGED_FILES" | grep '\.py$' || true)
+          if [ -z "$PY_FILES" ]; then
+            echo "No Python files changed."
+            exit 0
+          fi
+          echo "Checking Python syntax on:"
+          echo "$PY_FILES"
+          echo "$PY_FILES" | while IFS= read -r f; do
+            python3 -m py_compile "$f" || { echo "FAIL: syntax error in $f"; exit 1; }
+          done
+          echo "PASS: Python syntax"
+
+      - name: Secret scan
+        if: steps.changes.outputs.changed != ''
+        run: |
+          CHANGED_FILES="${{ steps.changes.outputs.changed }}"
+          SCAN_FILES=$(echo "$CHANGED_FILES" | grep -E '\.(py|yaml|yml|sh|json)$' || true)
+          if [ -z "$SCAN_FILES" ]; then
+            echo "No files to scan for secrets."
+            exit 0
+          fi
+          echo "Scanning files for secrets:"
+          echo "$SCAN_FILES"
+          if echo "$SCAN_FILES" | xargs -r grep -E 'sk-or-|sk-ant-|ghp_|AKIA' 2>/dev/null | \
+               grep -v '.gitea' | grep -v 'detect_secrets' | grep -v 'test_trajectory_sanitize' | grep -v 'test_secret_detection' | grep -q .; then
+            echo "FAIL: Secrets or hardcoded tokens detected"
+            exit 1
+          fi
+          echo "PASS: No secrets detected"
+
+      - name: Markdown sanity check
+        if: steps.changes.outputs.changed != ''
+        run: |
+          CHANGED_FILES="${{ steps.changes.outputs.changed }}"
+          MD_FILES=$(echo "$CHANGED_FILES" | grep '\.md$' || true)
+          if [ -z "$MD_FILES" ]; then
+            echo "No markdown files changed."
+            exit 0
+          fi
+          echo "Checking markdown sanity on:"
+          echo "$MD_FILES"
+          echo "$MD_FILES" | while IFS= read -r f; do
+            if [ ! -s "$f" ]; then
+              echo "FAIL: empty markdown file: $f"
+              exit 1
+            fi
+            if ! grep -q '[^[:space:]]' "$f"; then
+              echo "FAIL: markdown file contains only whitespace: $f"
+              exit 1
+            fi
+          done
+          echo "PASS: Markdown sanity"

README.md

@@ -99,6 +99,19 @@ python3 scripts/detect_secrets.py /tmp/test_secret.py
 # Should report: OpenAI API key detected
 ```
 
+
+## CI / PR Gate
+
+A lightweight minimum PR gate runs automatically on every pull request targeting `main`. The gate performs:
+
+- **Python syntax**: All changed Python files must compile without errors.
+- **Secret scan**: Changed code files are scanned for common hardcoded tokens (OpenAI, Anthropic, GitHub, AWS keys).
+- **Markdown sanity**: Changed Markdown documentation files must be non‑empty and contain meaningful text.
+
+The workflow is defined in `.gitea/workflows/minimum-pr-gate.yml`. It can also be triggered manually from the *Actions* panel (workflow_dispatch).
+
+This gate protects the repository from introducing broken code, leaked credentials, or empty documentation.
+
 ## Development
 
 ### Running Tests