docs: update Phase 3 status to completed in multi-provider architecture plan

Phase 3 Enhanced Makefile Commands has been completed with:
- Parameter validation for all infrastructure commands
- Provider discovery (infra-providers command)
- Environment listing (infra-environments command)
- Provider information display (provider-info command)
- Robust error handling for invalid parameters
- Enhanced user experience with clear error messages

All Phase 3 objectives achieved and tested.

Author: josecelano

docs/plans/multi-provider-architecture-plan.md

@@ -8,11 +8,11 @@ unlimited providers without code changes.
 
 ## Implementation Status
 
-### Current Status: PHASE 2 COMPLETED ✅
+### Current Status: PHASE 3 COMPLETED ✅
 
 - ✅ **Phase 1**: Foundation - Rename and Restructure (COMPLETED)
 - ✅ **Phase 2**: Provider System Implementation (COMPLETED)
-- ⏸️ **Phase 3**: Enhanced Makefile and Commands (IN PROGRESS)
+- ✅ **Phase 3**: Enhanced Makefile and Commands (COMPLETED)
 - ⏸️ **Phase 4**: Hetzner Provider Implementation (PLANNED)
 - ⏸️ **Phase 5**: Testing and Documentation (PLANNED)
 
@@ -34,6 +34,16 @@ unlimited providers without code changes.
 - ✅ **Security Improvements**: No hardcoded SSH keys, auto-detection from user's ~/.ssh/
 - ✅ **Integration Points**: PROVIDER parameter support in Makefile commands
 
+#### Phase 3 Completed (August 1, 2025)
+
+- ✅ **Enhanced Makefile Commands**: Parameter validation for all infrastructure commands
+- ✅ **Provider Discovery**: `infra-providers` command lists available providers
+- ✅ **Environment Listing**: `infra-environments` command shows available environments
+- ✅ **Provider Information**: `provider-info` command displays detailed provider configuration
+- ✅ **Parameter Validation**: Robust error handling for invalid provider/environment combinations
+- ✅ **User Experience**: Clear error messages and usage examples
+- ✅ **Command Integration**: All infrastructure commands use `check-infra-params` validation
+
 #### Current File Structure
 
 ```text
@@ -351,7 +361,7 @@ make test-e2e                                              # ✅ PASSES (~2m 35s
 
 ---
 
-### Phase 3: Enhanced Makefile and Commands ⏸️ IN PROGRESS
+### Phase 3: Enhanced Makefile and Commands ✅ COMPLETED
 
     # Load environment configuration
     load_environment
@@ -405,11 +415,11 @@ make infra-destroy ENVIRONMENT=development PROVIDER=libvirt
 
 ---
 
-### Phase 3: Enhanced Makefile and Commands ⏸️ IN PROGRESS
+### Phase 3: Enhanced Makefile and Commands ✅ COMPLETED
 
-**Current Status**: Basic PROVIDER parameter support implemented, full provider discovery pending.
+**Status**: All enhanced commands implemented with parameter validation and provider discovery.
 
-#### 3.1 Provider-Aware Makefile ✅ PARTIALLY IMPLEMENTED
+#### 3.1 Provider-Aware Makefile ✅ COMPLETED
 
 **Current working commands**:
 
@@ -512,9 +522,9 @@ make test-e2e  # Completes in ~2m 35s
 
 ### Next Immediate Steps
 
-1. **Complete Phase 3**: Implement provider discovery and enhanced Makefile commands
-2. **Hetzner Provider**: Begin Phase 4 implementation for cloud deployment
-3. **Documentation**: Update all guides to reflect new ENVIRONMENT/PROVIDER pattern
+1. **Begin Phase 4**: Implement Hetzner provider for cloud deployment
+2. **Phase 5 Planning**: Document all provider implementations and testing strategies
+3. **Documentation**: Update all guides to reflect enhanced command interface
 
 ## Benefits of Current Implementation