feat: Advanced Batch Orchestration with Enterprise-grade Error Handling

## Overview
Extend the Batch Script Mode to provide sophisticated error handling, advanced orchestration patterns, and workflow management capabilities. This enhancement will transform bssh into a comprehensive cluster orchestration platform while maintaining backward compatibility with simple scripts. The system will support complex deployment patterns, sophisticated error recovery mechanisms, and enterprise-grade workflow management.

## Technical Approach

Building upon the batch script foundation, we'll add:

### 1. Error Handling Framework
- Multi-level error strategies (node, stage, script)
- Error recovery mechanisms with automatic retry and fallback
- Rollback orchestration with state snapshots
- Circuit breaker patterns for failing nodes

### 2. Orchestration Engine
- Dependency graph execution with topological sorting
- Wave-based execution with configurable parallelism
- Leader election and distributed coordination
- Event-driven workflow transitions

### 3. Workflow Management System
- State machine-based workflow engine
- Checkpoint and resume capabilities
- Workflow composition and inheritance
- Real-time workflow monitoring and control

### 4. Dynamic Node Management
- Runtime node addition/removal
- Auto-discovery with health checks
- Load balancing and failover
- Node tagging and dynamic groups

## Key Features

### Enhanced Error Handling
- **Threshold-Based Strategy**: Stop if failure rate exceeds percentage/count
- **Circuit Breaker**: Temporarily exclude failing nodes after repeated failures
- **Exponential Backoff**: Smart retry with jitter to prevent thundering herd
- **Rollback Mechanism**: Transaction-like semantics with commit/rollback
- **Dead Letter Queue**: For permanently failed operations

### Advanced Orchestration Patterns
- **Canary Deployment**: Gradual rollout with validation gates
- **Blue-Green Deployment**: Zero-downtime deployments with instant rollback
- **Rolling Update**: Configurable batch sizes and validation between waves
- **Dependency Graph**: Complex service dependencies with topological execution
- **Leader Election**: Raft-based consensus for critical operations

### Workflow Management
- **Checkpointing**: Periodic state snapshots for resume capability
- **Workflow States**: Pending, Running, Paused, Failed, Completed with transitions
- **Composition**: Template workflows with inheritance and parameterization
- **Control Plane**: Start, pause, resume, cancel operations with monitoring

## Implementation Phases

### Phase 1: Enhanced Error Handling Framework
- [ ] Create error handling module with multiple strategies
- [ ] Implement per-node error tracking with health scores
- [ ] Build configurable failure strategies (FailFast, Continue, Threshold)
- [ ] Create rollback mechanism with compensating actions
- [ ] Implement retry orchestration with various policies

### Phase 2: Advanced Orchestration Features
- [ ] Build dependency graph executor with topological sorting
- [ ] Implement staged execution with wave-based deployment
- [ ] Create leader election system using Raft consensus
- [ ] Build coordination service for distributed operations
- [ ] Add health check framework for continuous validation

### Phase 3: Workflow Management System
- [ ] Design workflow state machine with transition rules
- [ ] Implement checkpoint system with state persistence
- [ ] Build workflow patterns (canary, blue-green, rolling)
- [ ] Create workflow composition with inheritance
- [ ] Add workflow control plane for runtime management

### Phase 4: Node-Specific Script Management
- [ ] Implement role-based scripts with capabilities
- [ ] Build template system with property interpolation
- [ ] Create script generation engine for dynamic creation
- [ ] Add script distribution with compression and verification

### Phase 5: Dynamic Node Management
- [ ] Implement node discovery (service discovery, DNS, cloud APIs)
- [ ] Build node lifecycle management with onboarding/decommissioning
- [ ] Create load balancing strategies (round-robin, weighted, least connections)
- [ ] Implement failover mechanism with split-brain prevention

### Phase 6: Enhanced Error Reporting and Monitoring
- [ ] Build comprehensive reporting with analytics
- [ ] Implement detailed logging with correlation IDs
- [ ] Create alerting system with escalation
- [ ] Add metrics collection for observability

## Example: Complex Production Deployment

```yaml
name: Production Deployment Pipeline
version: 2.0

orchestration:
error_handling:
strategy: adaptive
checkpoint_interval: 5m

node_management:
discovery:
method: service_registry
refresh_interval: 30s

workflow:
- stage: canary_deployment
nodes:
selector: "role=web && canary=true"
count: 2
steps:
- name: deploy_application
upload: "dist/" to: "/app/new/"
command: |
ln -sfn /app/new /app/current
systemctl restart webapp

- name: validate_canary
wait: 30s
validations:
- http_check:
url: "http://localhost/health"
expected_status: 200
- error_rate:
threshold: 1%
duration: 5m

- stage: gradual_rollout
depends_on: [canary_deployment]
waves:
count: 4 # 25% each wave
delay: 5m
on_wave_failure: pause
nodes: "role=web && canary=false"
steps:
- name: deploy_wave
parallel: 10
command: |
ln -sfn /app/new /app/current
systemctl restart webapp
```

## Performance and Scalability Targets
- Support 10,000+ nodes in a single cluster
- Execute 1,000+ parallel operations
- Handle 100+ concurrent workflows
- Process 1M+ operations per hour
- Maintain <100ms operation latency at scale

## Security Enhancements
- Script signing and verification
- Role-based access control (RBAC)
- Audit logging for compliance
- Secrets management integration
- Sandboxed execution with resource limits

## New Dependencies
```toml
# Error handling and resilience
backoff = "0.4" # Exponential backoff
circuit-breaker = "0.2" # Circuit breaker pattern

# Orchestration
petgraph = "0.6" # Dependency graph management
raft = "0.7" # Leader election

# Workflow management
rocksdb = "0.22" # State persistence

# Monitoring
prometheus = "0.13" # Metrics
opentelemetry = "0.26" # Tracing

# Security
ring = "0.17" # Cryptographic signing
jsonwebtoken = "9.3" # Token validation
```

## Success Criteria
- 99.9% reliability for critical operations
- <1s latency for operation initiation
- Support 100+ concurrent workflows
- Recovery from checkpoint in <30s
- Comprehensive audit trail for compliance
- 90%+ test coverage
- Zero critical security vulnerabilities
- <0.1% failure rate in production

## Benefits
1. **Enterprise-grade reliability** with sophisticated error handling
2. **Complex deployment support** with orchestration patterns
3. **Operational excellence** through workflow management
4. **Elastic infrastructure** with dynamic node management
5. **Complete observability** with monitoring and alerting
6. **Regulatory compliance** with audit trails and rollback

## Related Work
- Original task document: `.claude/tasks/todo/3_enhanced_batch_orchestration.md`
- Builds upon: Batch Script Mode (#13)