fix: anthropic messages validation, stream mapping, client error parsing, and add Cloudflare Workers deployment workflow

- Fix type mappings in OpenAIRequest and BackendConfig to handle structured message parts (cache-control).
- Stop adaptRequest crashing when message contents are objects or arrays.
- Forward stream, top_k, and stop_sequences to adaptRequest.
- Forward anthropic-version header to backend endpoints during adaptation.
- Parse structured JSON error payloads from upstream before returning generic "Upstream rejected request" error.
- Create .github/workflows/cloudflare.yml to auto-deploy on master branch pushes.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

.github/workflows/cloudflare.yml

@@ -0,0 +1,32 @@
+name: Deploy to Cloudflare Workers
+
+on:
+  push:
+    branches:
+      - master
+  workflow_dispatch:
+
+jobs:
+  deploy:
+    name: Deploy to Cloudflare Workers
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout Code
+        uses: actions/checkout@v4
+
+      - name: Setup Bun
+        uses: oven-sh/setup-bun@v2
+        with:
+          bun-version: latest
+
+      - name: Install Dependencies
+        run: bun install --frozen-lockfile
+
+      - name: Run Tests
+        run: bun test
+
+      - name: Deploy Worker
+        uses: cloudflare/wrangler-action@v3
+        with:
+          apiToken: ${{ secrets.CLOUDFLARE_API_TOKEN }}
+          command: deploy