feat: initial Argus - AI-powered FinOps agent

Argus is an all-seeing eye on your AWS costs:
- Scan for optimization opportunities (unused resources, oversized instances)
- Evaluate Terraform plans for cost impact
- Generate weekly/monthly cost reports
- Integrate with Atlantis for pre-apply cost analysis

Components:
- CLI tool (argus scan/evaluate/report)
- GitHub Action for CI/CD integration
- AWS Scanner for resource analysis
- AI engine for intelligent recommendations

Features:
- Unused EBS volumes, idle EC2, oversized RDS
- Cost delta on Terraform changes
- Atlantis integration
- Slack/email notifications

action/action.yml

@@ -0,0 +1,138 @@
+name: 'Argus FinOps'
+description: 'AI-powered cost analysis for AWS infrastructure'
+author: 'ghndrx'
+
+branding:
+  icon: 'dollar-sign'
+  color: 'green'
+
+inputs:
+  mode:
+    description: 'Operation mode: scan, evaluate, or report'
+    required: true
+    default: 'evaluate'
+  
+  plan-file:
+    description: 'Terraform plan file (for evaluate mode)'
+    required: false
+  
+  regions:
+    description: 'AWS regions to scan (comma-separated)'
+    required: false
+    default: 'us-east-1'
+  
+  period:
+    description: 'Report period: daily, weekly, monthly'
+    required: false
+    default: 'weekly'
+  
+  ai-provider:
+    description: 'AI provider: bedrock or openai'
+    required: false
+    default: 'bedrock'
+  
+  ai-model:
+    description: 'AI model ID'
+    required: false
+    default: 'anthropic.claude-3-5-sonnet-20241022-v2:0'
+  
+  comment-on-pr:
+    description: 'Comment results on PR'
+    required: false
+    default: 'true'
+  
+  fail-on-increase:
+    description: 'Fail if cost increases above threshold'
+    required: false
+    default: 'false'
+  
+  fail-threshold:
+    description: 'Cost increase threshold (monthly $)'
+    required: false
+    default: '100'
+  
+  slack-webhook:
+    description: 'Slack webhook for notifications'
+    required: false
+  
+  output-format:
+    description: 'Output format: markdown, json, github'
+    required: false
+    default: 'github'
+
+outputs:
+  monthly-delta:
+    description: 'Monthly cost change in dollars'
+  
+  total-savings:
+    description: 'Total potential savings identified'
+  
+  findings-count:
+    description: 'Number of optimization findings'
+  
+  report:
+    description: 'Full report content'
+
+runs:
+  using: 'composite'
+  steps:
+    - name: Setup Python
+      uses: actions/setup-python@v5
+      with:
+        python-version: '3.11'
+    
+    - name: Install Argus
+      shell: bash
+      run: |
+        pip install boto3 requests
+        # In production: pip install argus-finops
+    
+    - name: Run Argus
+      id: argus
+      shell: bash
+      env:
+        ARGUS_AI_PROVIDER: ${{ inputs.ai-provider }}
+        ARGUS_AI_MODEL: ${{ inputs.ai-model }}
+      run: |
+        case "${{ inputs.mode }}" in
+          scan)
+            python -m argus scan \
+              --regions ${{ inputs.regions }} \
+              --output-format ${{ inputs.output-format }} \
+              --output /tmp/argus-report.md
+            ;;
+          evaluate)
+            python -m argus evaluate \
+              --plan-file "${{ inputs.plan-file }}" \
+              --output-format ${{ inputs.output-format }} \
+              --output /tmp/argus-report.md \
+              ${{ inputs.fail-on-increase == 'true' && '--fail-on-increase' || '' }} \
+              --fail-threshold ${{ inputs.fail-threshold }}
+            ;;
+          report)
+            python -m argus report \
+              --period ${{ inputs.period }} \
+              --regions ${{ inputs.regions }} \
+              --output-format ${{ inputs.output-format }} \
+              --output /tmp/argus-report.md \
+              ${{ inputs.slack-webhook && format('--slack-webhook {0}', inputs.slack-webhook) || '' }}
+            ;;
+        esac
+        
+        # Set outputs
+        echo "report<<EOF" >> $GITHUB_OUTPUT
+        cat /tmp/argus-report.md >> $GITHUB_OUTPUT
+        echo "EOF" >> $GITHUB_OUTPUT
+    
+    - name: Comment on PR
+      if: inputs.comment-on-pr == 'true' && github.event_name == 'pull_request'
+      uses: actions/github-script@v7
+      with:
+        script: |
+          const report = `${{ steps.argus.outputs.report }}`;
+          github.rest.issues.createComment({
+            issue_number: context.issue.number,
+            owner: context.repo.owner,
+            repo: context.repo.repo,
+            body: `## 💰 Argus Cost Analysis\n\n${report}`
+          });