fix: Update deprecated GitHub Actions to latest versions

Updated all GitHub Actions to resolve deprecation warnings and failures:

**Actions Updated:**
- actions/checkout: v3 → v4 (5 instances)
- actions/setup-python: v4 → v5 (5 instances)
- actions/upload-artifact: v3 → v4 (1 instance)

**Root Cause:**
GitHub deprecated v3 of artifact actions on April 16, 2024. Workflows
using the old versions now fail with:
"This request has been automatically failed because it uses a
deprecated version of actions/upload-artifact: v3"

**Changes:**
- ci.yml: Updated checkout and setup-python actions
- harmony-check.yml: Updated all actions across 4 jobs:
  * Job 1: harmony-check
  * Job 2: harmony-json-report (includes upload-artifact fix)
  * Job 3: harmony-strict-check
  * Job 4: harmony-exit-codes-demo

**Benefits:**
- ✅ Resolves workflow failures from deprecated actions
- ✅ Uses latest stable action versions with improvements
- ✅ Future-proofs CI/CD pipeline
- ✅ Maintains backward compatibility with Python 3.8-3.12

**Testing:**
- ✅ YAML syntax validates successfully
- ✅ All action versions verified as latest stable

Reference: https://github.blog/changelog/2024-04-16-deprecation-notice-v3-of-the-artifact-actions/

Author: claude

.github/workflows/ci.yml

@@ -12,10 +12,10 @@ jobs:
         python-version: ["3.8", "3.9", "3.10", "3.11", "3.12"]
 
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
 
       - name: Set up Python ${{ matrix.python-version }}
-        uses: actions/setup-python@v4
+        uses: actions/setup-python@v5
         with:
           python-version: ${{ matrix.python-version }}
 

.github/workflows/harmony-check.yml

@@ -13,10 +13,10 @@ jobs:
 
     steps:
       - name: Checkout code
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
 
       - name: Set up Python
-        uses: actions/setup-python@v4
+        uses: actions/setup-python@v5
         with:
           python-version: '3.11'
 
@@ -59,10 +59,10 @@ jobs:
 
     steps:
       - name: Checkout code
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
 
       - name: Set up Python
-        uses: actions/setup-python@v4
+        uses: actions/setup-python@v5
         with:
           python-version: '3.11'
 
@@ -104,7 +104,7 @@ jobs:
           fi
 
       - name: Upload JSON Report as Artifact
-        uses: actions/upload-artifact@v3
+        uses: actions/upload-artifact@v4
         with:
           name: harmony-report
           path: harmony-report.json
@@ -150,10 +150,10 @@ jobs:
 
     steps:
       - name: Checkout code
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
 
       - name: Set up Python
-        uses: actions/setup-python@v4
+        uses: actions/setup-python@v5
         with:
           python-version: '3.11'
 
@@ -186,10 +186,10 @@ jobs:
 
     steps:
       - name: Checkout code
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
 
       - name: Set up Python
-        uses: actions/setup-python@v4
+        uses: actions/setup-python@v5
         with:
           python-version: '3.11'