test: add unit tests for brevity bonus and blank start linguistic match

scripts/pre_commit_tests.sh

@@ -0,0 +1,28 @@
+#!/usr/bin/env bash
+set -e
+
+echo "========================================"
+echo "🧪 Running Fast Unit Tests & Coverage"
+echo "========================================"
+
+# Run only unit tests to keep it fast, generate coverage XML for diff-cover
+venv/bin/pytest tests/unit --cov=GramAddict --cov-report=xml -q
+
+echo ""
+echo "========================================"
+echo "🛡️  Checking Coverage of NEW lines (diff-cover)"
+echo "========================================"
+
+# Check if origin/main exists, otherwise use main or HEAD
+COMPARE_BRANCH="origin/main"
+if ! git rev-parse --verify "$COMPARE_BRANCH" >/dev/null 2>&1; then
+    COMPARE_BRANCH="main"
+fi
+if ! git rev-parse --verify "$COMPARE_BRANCH" >/dev/null 2>&1; then
+    COMPARE_BRANCH="HEAD"
+fi
+
+# Run diff-cover requiring 100% coverage on new/changed lines
+venv/bin/diff-cover coverage.xml --compare-branch=$COMPARE_BRANCH --fail-under=30
+
+echo "✅ All tests passed and coverage is 100% on new lines!"