debug: add gdb workflow to capture kuzu SIGSEGV backtrace

Temporary workflow_dispatch job: runs the suite under gdb on ubuntu-latest to capture the C-level backtrace of the segfault at ~53% (ladybug's bundled kuzu). Safe to delete once root-caused.

Co-Authored-By: Claude <noreply@anthropic.com>

Author: HumanBean17

.github/workflows/debug-segfault.yml

@@ -0,0 +1,63 @@
+name: debug-segfault
+
+# TEMPORARY: capture the C-level backtrace of the kuzu SIGSEGV that test.yml
+# hits at ~53% (tests/test_ladybug_queries.py::test_find_by_name_or_fqn_simple_name
+# -> ladybug.connection._execute_with_pybind). The crash only reproduces on real
+# x86_64 (not on macOS Docker), so we run under gdb here. Delete this file once
+# the root cause is found.
+on:
+  workflow_dispatch:
+
+jobs:
+  gdb:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+      - uses: actions/setup-python@v5
+        with:
+          python-version: "3.11"
+      - name: Install gdb
+        run: sudo apt-get update && sudo apt-get install -y gdb
+      - name: Cache HuggingFace models
+        uses: actions/cache@v4
+        with:
+          path: ~/.cache/huggingface
+          key: hf-${{ hashFiles('**/pyproject.toml') }}-v1
+          restore-keys: |
+            hf-${{ hashFiles('**/pyproject.toml') }}-
+            hf-
+      - name: Install dependencies
+        run: |
+          python -m pip install --upgrade pip
+          pip install -e ".[dev]"
+      - name: Run suite under gdb (capture kuzu SIGSEGV backtrace)
+        continue-on-error: true
+        env:
+          JAVA_CODEBASE_RAG_RUN_HEAVY: "0"
+          HF_TOKEN: ${{ secrets.HF_TOKEN }}
+          TRANSFORMERS_CACHE: ~/.cache/huggingface
+          HF_HOME: ~/.cache/huggingface
+          PYTHONFAULTHANDLER: "1"
+        run: |
+          gdb -q -batch \
+            -ex "set pagination off" \
+            -ex "set print thread-events off" \
+            -ex "run" \
+            -ex "echo \n========== GDB: ALL THREADS BACKTRACE ==========\n" \
+            -ex "thread apply all bt" \
+            --args python -m pytest tests -v 2>&1 | tee gdb-output.log
+          echo "gdb finished (inferior exit ${PIPESTATUS[0]}; 139 = SIGSEGV expected)"
+      - name: Show crash location
+        if: always()
+        run: |
+          echo "=== signal / fault markers ==="
+          grep -nE "Fatal Python error|Segmentation fault|received signal SIGSEGV|Program terminated" gdb-output.log | head || true
+          echo "=== gdb backtrace (first 150 lines after marker) ==="
+          awk '/GDB: ALL THREADS BACKTRACE/{f=1} f{print; if(++n>150) exit}' gdb-output.log || true
+      - uses: actions/upload-artifact@v4
+        if: always()
+        with:
+          name: gdb-output
+          path: gdb-output.log