feat(ci): add 20% coverage threshold and terminal coverage report (#18)

Baseline coverage is 30%. Set threshold at 20% with buffer.
Add --cov-report=term for visible coverage in CI logs.

Closes #17

Co-authored-by: gss <tbag9199@gmail.com>
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: 3 people

.github/workflows/ci.yml

@@ -49,7 +49,7 @@ jobs:
       - run: pip install -e ".[dev]" pytest-cov
         env:
           PIP_INDEX_URL: https://pypi.org/simple
-      - run: pytest -v --tb=short --cov=narrator_ai --cov-report=xml
+      - run: pytest -v --tb=short --cov=narrator_ai --cov-report=term --cov-report=xml --cov-fail-under=20
 
   security:
     name: Security Scan