feat(phase9): implement WebSocket transport and failover system

Implements Phase 9: Remoting / Cloud Hybrid Deployment with complete
WebSocket transport support and comprehensive failover mechanisms.

**WebSocket Transport (remote_client.rs):**
- Added WebSocket support to RemoteMcpClient using tokio-tungstenite
- Full bidirectional JSON-RPC communication over WebSocket
- Connection establishment with error handling
- Text/binary message support with proper encoding
- Connection closure detection and error reporting

**Failover & Redundancy (failover.rs - 323 lines):**
- ServerHealth tracking: Healthy, Degraded, Down states
- ServerEntry with priority-based selection (lower = higher priority)
- FailoverMcpClient implementing McpClient trait
- Automatic retry with exponential backoff
- Circuit breaker pattern (5 consecutive failures triggers Down state)
- Background health checking with configurable intervals
- Graceful failover through server priority list

**Configuration:**
- FailoverConfig with tunable parameters:
  - max_retries: 3 (default)
  - base_retry_delay: 100ms with exponential backoff
  - health_check_interval: 30s
  - circuit_breaker_threshold: 5 failures

**Testing (phase9_remoting.rs - 9 tests, all passing):**
- Priority-based server selection
- Automatic failover to backup servers
- Retry mechanism with exponential backoff
- Health status tracking and transitions
- Background health checking
- Circuit breaker behavior
- Error handling for edge cases

**Dependencies:**
- tokio-tungstenite 0.21
- tungstenite 0.21

All tests pass successfully. Phase 9 specification fully implemented.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

crates/owlen-core/src/tools.rs

@@ -8,6 +8,7 @@
 pub mod code_exec;
 pub mod fs_tools;
 pub mod registry;
+pub mod web_scrape;
 pub mod web_search;
 pub mod web_search_detailed;
 
@@ -91,5 +92,6 @@ impl ToolResult {
 pub use code_exec::CodeExecTool;
 pub use fs_tools::{ResourcesDeleteTool, ResourcesGetTool, ResourcesListTool, ResourcesWriteTool};
 pub use registry::ToolRegistry;
+pub use web_scrape::WebScrapeTool;
 pub use web_search::WebSearchTool;
 pub use web_search_detailed::WebSearchDetailedTool;