feat: add browser automation tool using Vercel agent-browser

- Add src/tools/browser.rs with BrowserTool implementation
- Wraps agent-browser CLI for AI-optimized web browsing
- Supports: open, snapshot, click, fill, type, screenshot, wait, etc.
- Uses refs (@e1, @e2) from accessibility snapshots for precise element selection
- JSON output mode for LLM integration
- Security: allowlist-only domains, blocks private/local hosts
- Add session_name to BrowserConfig for persistent sessions
- Register BrowserTool in tools/mod.rs alongside BrowserOpenTool

All tests pass.

Dockerfile

@@ -13,12 +13,29 @@ FROM gcr.io/distroless/cc-debian12:nonroot
 
 COPY --from=builder /app/target/release/zeroclaw /usr/local/bin/zeroclaw
 
-# Default workspace (owned by nonroot user)
-VOLUME ["/workspace"]
-ENV ZEROCLAW_WORKSPACE=/workspace
+# Default workspace and data directory (owned by nonroot user)
+VOLUME ["/data"]
+ENV ZEROCLAW_WORKSPACE=/data/workspace
+
+# ── Environment variable configuration (Docker-native setup) ──
+# These can be overridden at runtime via docker run -e or docker-compose
+#
+# Required:
+#   API_KEY or ZEROCLAW_API_KEY     - Your LLM provider API key
+#
+# Optional:
+#   PROVIDER or ZEROCLAW_PROVIDER   - LLM provider (default: openrouter)
+#                                     Options: openrouter, openai, anthropic, ollama
+#   ZEROCLAW_MODEL                  - Model to use (default: anthropic/claude-sonnet-4-20250514)
+#   PORT or ZEROCLAW_GATEWAY_PORT   - Gateway port (default: 3000)
+#
+# Example:
+#   docker run -e API_KEY=sk-... -e PROVIDER=openrouter zeroclaw/zeroclaw
 
 # Explicitly set non-root user (distroless:nonroot defaults to 65534, but be explicit)
 USER 65534:65534
 
+EXPOSE 3000
+
 ENTRYPOINT ["zeroclaw"]
 CMD ["gateway"]