Complete notification system implementation with 9 channels, reliability features, and comprehensive testing

Implemented complete notification system following IMPLEMENTATION_ROADMAP.md:

**Notification Channels (9 total):**
- Slack, Discord, Telegram
- Email (SMTP), Generic Webhook, MS Teams
- PagerDuty, Jira, GitHub Issues

**Reliability Features:**
- Retry mechanism with exponential backoff
- Rate limiting with token bucket algorithm
- Notification queue with worker pool
- Comprehensive metrics tracking

**Event System:**
- Event bus with sync/async modes (84.5% test coverage)
- Event-driven notification handler
- 29 event types (task, workflow, worker, system)

**Testing Infrastructure:**
- Mock servers for Slack, Telegram, Discord (100% coverage)
- 40+ performance benchmarks
- 7 load tests (1000+/sec throughput)
- Integration tests for all channels
- CI/CD workflow with GitHub Actions

**Documentation:**
- API Reference (438 lines)
- Configuration Reference (800+ lines)
- Performance Guide (700+ lines)
- Testing Guide (500+ lines)
- Event Integration Guide

**Test Coverage:**
- Notification package: 48.1%
- Event package: 84.5%
- Mock servers: 100%
- All tests passing

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

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

Author: milos85vasic

.github/workflows/notification-tests.yml

@@ -0,0 +1,118 @@
+name: Notification Tests
+
+on:
+  push:
+    branches: [ main, develop ]
+    paths:
+      - 'HelixCode/internal/notification/**'
+      - 'HelixCode/test/integration/**'
+      - '.github/workflows/notification-tests.yml'
+  pull_request:
+    branches: [ main, develop ]
+    paths:
+      - 'HelixCode/internal/notification/**'
+      - 'HelixCode/test/integration/**'
+      - '.github/workflows/notification-tests.yml'
+
+jobs:
+  unit-tests:
+    name: Unit Tests
+    runs-on: ubuntu-latest
+
+    steps:
+    - name: Checkout code
+      uses: actions/checkout@v4
+
+    - name: Set up Go
+      uses: actions/setup-go@v5
+      with:
+        go-version: '1.24.0'
+        cache-dependency-path: HelixCode/go.sum
+
+    - name: Install dependencies
+      working-directory: ./HelixCode
+      run: go mod download
+
+    - name: Run unit tests
+      working-directory: ./HelixCode
+      run: |
+        go test ./internal/notification/... -v -cover -coverprofile=coverage.out -covermode=atomic
+
+    - name: Generate coverage report
+      working-directory: ./HelixCode
+      run: |
+        go tool cover -func=coverage.out
+
+    - name: Upload coverage to Codecov
+      uses: codecov/codecov-action@v4
+      with:
+        files: ./HelixCode/coverage.out
+        flags: notifications
+        name: notification-coverage
+        fail_ci_if_error: false
+
+  integration-tests:
+    name: Integration Tests
+    runs-on: ubuntu-latest
+
+    steps:
+    - name: Checkout code
+      uses: actions/checkout@v4
+
+    - name: Set up Go
+      uses: actions/setup-go@v5
+      with:
+        go-version: '1.24.0'
+        cache-dependency-path: HelixCode/go.sum
+
+    - name: Install dependencies
+      working-directory: ./HelixCode
+      run: go mod download
+
+    - name: Run integration tests
+      working-directory: ./HelixCode
+      run: |
+        go test ./test/integration/... -v -tags=integration -timeout=5m
+
+  lint:
+    name: Lint
+    runs-on: ubuntu-latest
+
+    steps:
+    - name: Checkout code
+      uses: actions/checkout@v4
+
+    - name: Set up Go
+      uses: actions/setup-go@v5
+      with:
+        go-version: '1.24.0'
+        cache-dependency-path: HelixCode/go.sum
+
+    - name: Run golangci-lint
+      uses: golangci/golangci-lint-action@v4
+      with:
+        version: latest
+        working-directory: HelixCode
+        args: --timeout=5m ./internal/notification/...
+
+  test-summary:
+    name: Test Summary
+    runs-on: ubuntu-latest
+    needs: [unit-tests, integration-tests, lint]
+    if: always()
+
+    steps:
+    - name: Check test results
+      run: |
+        echo "Unit Tests: ${{ needs.unit-tests.result }}"
+        echo "Integration Tests: ${{ needs.integration-tests.result }}"
+        echo "Lint: ${{ needs.lint.result }}"
+
+        if [ "${{ needs.unit-tests.result }}" != "success" ] || \
+           [ "${{ needs.integration-tests.result }}" != "success" ] || \
+           [ "${{ needs.lint.result }}" != "success" ]; then
+          echo "❌ Some tests failed"
+          exit 1
+        else
+          echo "✅ All tests passed"
+        fi