feat: add shared ruff config + downstream CI trigger

- ruff-shared.toml: unified lint rules for all QSL repos
- trigger-downstream-ci.yml: QPK changes → auto-trigger platform CIs
- Prevents QPK SHA drift by validating all consumers on every push

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

Author: Pigbibi

.github/workflows/trigger-downstream-ci.yml

@@ -0,0 +1,37 @@
+name: Trigger Downstream CI
+
+on:
+  push:
+    branches: [ main ]
+    paths-ignore:
+      - "docs/**"
+      - "**.md"
+      - "QPK_PIN"
+      - "constraints.txt"
+
+permissions:
+  actions: write
+
+jobs:
+  trigger:
+    runs-on: ubuntu-latest
+    timeout-minutes: 10
+    strategy:
+      max-parallel: 5
+      matrix:
+        repo:
+          - QuantStrategyLab/InteractiveBrokersPlatform
+          - QuantStrategyLab/LongBridgePlatform
+          - QuantStrategyLab/CharlesSchwabPlatform
+          - QuantStrategyLab/FirstradePlatform
+          - QuantStrategyLab/UsEquityStrategies
+          - QuantStrategyLab/HkEquityStrategies
+          - QuantStrategyLab/CnEquityStrategies
+          - QuantStrategyLab/CryptoStrategies
+          - QuantStrategyLab/UsEquitySnapshotPipelines
+    steps:
+      - name: Trigger ${{ matrix.repo }} CI
+        run: |
+          gh workflow run ci.yml --repo "${{ matrix.repo }}" --ref main || true
+        env:
+          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}