Fix GitLab CI for shell executor: use python3 and venv

.gitlab-ci.yml

@@ -1,30 +1,24 @@
 # GitLab CI/CD Pipeline for OpenCompletion
-# Mirrors GitHub Actions workflow for consistency across platforms
+# Uses shell executor on build-tagged runners
 
 stages:
   - test
   - lint
 
 variables:
-  PIP_CACHE_DIR: "$CI_PROJECT_DIR/.cache/pip"
   SQLALCHEMY_DATABASE_URI: "sqlite:///:memory:"
   TESTING: "1"
   MODEL_ENDPOINT_0: "https://hermes.ai.unturf.com/v1"
   MODEL_API_KEY_0: "dummy"
 
-# Cache pip dependencies between jobs
-cache:
-  paths:
-    - .cache/pip
-    - venv/
-
-# Template for Python setup
+# Template for Python setup (shell executor)
 .python_setup:
-  image: python:3.13-slim
   tags:
     - build
   before_script:
-    - python -m pip install --upgrade pip
+    - python3 -m venv venv
+    - source venv/bin/activate
+    - python3 -m pip install --upgrade pip
     - pip install -r requirements.txt
     - pip install -r requirements-test.txt
 
@@ -33,18 +27,15 @@ unit_tests:
   extends: .python_setup
   stage: test
   script:
+    - source venv/bin/activate
     - pytest tests/unit/ -v --tb=short --cov=. --cov-report=term-missing
-  artifacts:
-    when: always
-    reports:
-      junit: report.xml
-    expire_in: 1 week
 
 # Functional Tests
 functional_tests:
   extends: .python_setup
   stage: test
   script:
+    - source venv/bin/activate
     - pytest tests/functional/ -v --tb=short
 
 # Integration Tests
@@ -52,6 +43,7 @@ integration_tests:
   extends: .python_setup
   stage: test
   script:
+    - source venv/bin/activate
     - pytest tests/integration/ -v --tb=short
 
 # Validate Activity YAML Files
@@ -59,29 +51,34 @@ validate_yaml:
   extends: .python_setup
   stage: test
   script:
+    - source venv/bin/activate
     - python activity_yaml_validator.py research/SPEC.yaml
     - python activity_yaml_validator.py research/activity*.yaml
 
 # Lint - Syntax Errors (blocking)
 lint_syntax:
-  image: python:3.13-slim
   stage: lint
   tags:
     - build
   before_script:
+    - python3 -m venv venv
+    - source venv/bin/activate
     - pip install flake8
   script:
+    - source venv/bin/activate
     - flake8 . --count --select=E9,F63,F7,F82 --show-source --statistics
 
 # Lint - Style Warnings (non-blocking)
 lint_style:
-  image: python:3.13-slim
   stage: lint
   tags:
     - build
   before_script:
+    - python3 -m venv venv
+    - source venv/bin/activate
     - pip install black flake8
   script:
+    - source venv/bin/activate
     - black --check --diff . || true
     - flake8 . --count --exit-zero --max-complexity=10 --max-line-length=127 --statistics
   allow_failure: true