feat(test): add developer quality gate consolidation (G-007)

- Add scripts/test-integration-fast.sh for fast integration tests
- Add scripts/test-coverage.sh with 12% baseline threshold
- Update Makefile with test-integration-fast, test-coverage, test-all-local
- Update CI workflow with integration and coverage jobs
- Add smoke marker to pytest.ini
- Update tests/README.md with quality gate layers documentation
- Add tests/integration/pipeline/ for pipeline stage-chain tests

Quality gate layers:
- Quick: ruff + unit + smoke (~2 min)
- Fast Integration: SQLite/API/Pipeline (~3 min)
- Coverage: 12% threshold gate (~8 min)
- Full Local: all three combined

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

scripts/test-integration-fast.sh

@@ -0,0 +1,16 @@
+#!/bin/bash
+
+# Fast integration tests
+# Runs integration tests excluding slow ones (PostgreSQL, external services)
+# Uses fake runner/provider, no real credentials needed
+
+set -euo pipefail
+
+echo "=== LangBot Fast Integration Tests ==="
+echo ""
+
+echo "Running integration tests (excluding slow)..."
+uv run pytest tests/integration/ -m "not slow" -q --tb=short
+
+echo ""
+echo "=== Fast Integration Tests Complete ==="