feat(qizheng): vendor stem-branch and expose three read-only chart APIs

Add Apache-2.0 @4n6h4x0r/stem-branch 0.8.0, a seven-governors adapter,
and POST /api/qizheng, /api/western, /api/ephemeris_events.

BUG-700 remains blocked (do not call --pillars). BUG-701 and BUG-702 are
resolved. BUG-703 is investigating (panchanga Lahiri). Skill is not bumped.

scripts/run_quality_gate.py

@@ -75,6 +75,11 @@ CORE_PYTEST_TARGETS = [
     "tests/test_birth_time_journey_contract.py",
     # Freeze scripts/jyotish_api_server.py growth; new features must be modules.
     "tests/test_api_server_growth_contract.py",
+    # Native seven-governors adapter and the three read-only chart endpoints.
+    "tests/test_qizheng_chart_engine.py",
+    "tests/test_qizheng_api_productization.py",
+    "tests/test_readonly_chart_endpoints.py",
+    "tests/test_ephemeris_events.py",
     # Fail-fast heavy-compute concurrency gate (429 + Retry-After, health ungated).
     "tests/test_api_heavy_compute_gate.py",
     # Upstream-sync acceptance regressions must fail the automatic staging gate.