conductor(gui_2): Phase 1 checkpoint — 3-file inventory + 4 invariant tests

TIER-2 READ conductor/code_styleguides/error_handling.md end-to-end before Phase 1.

Tasks:
- 1.1: Run audit --include-baseline --json > PHASE1_AUDIT_BASELINE.json
- 1.2: Walk audit + write 3 inventory docs (46+33+9 = 88 sites)
- 1.3: Add 4 Phase 1 invariant tests in tests/test_baseline_result.py

Per-file migration-target counts (from audit):
  mcp_client.py: 46 (40 BC + 5 SS + 1 UNCLEAR)
  ai_client.py:  33 (17 BC + 9 SS + 7 RETHROW)
  rag_engine.py:  9 ( 5 BC + 1 SS + 3 RETHROW)
  Total: 88 sites

Stay-as-is counts:
  mcp_client.py: 9 (all INTERNAL_COMPLIANT)
  ai_client.py: 26 (4 BOUNDARY_SDK + 4 INTERNAL_PROGRAMMER_RAISE + 17 COMPLIANT + 1 BOUNDARY_CONVERSION)
  rag_engine.py: 6 (5 INTERNAL_PROGRAMMER_RAISE + 1 COMPLIANT)

tests/test_baseline_result.py

@@ -0,0 +1,67 @@
+"""Phase 1 invariant tests for result_migration_baseline_cleanup_20260620.
+
+Asserts:
+1. The 3 baseline files have the expected site counts (audit per-file totals)
+2. Migration-target total = 88 (46 + 33 + 9)
+3. PHASE1_AUDIT_BASELINE.json + 3 inventory docs exist and have correct counts
+"""
+import json
+from collections import Counter
+from pathlib import Path
+
+import pytest
+
+
+AUDIT_PATH = Path("tests/artifacts/PHASE1_AUDIT_BASELINE.json")
+INV_MCP = Path("tests/artifacts/PHASE1_INVENTORY_mcp_client.md")
+INV_AI = Path("tests/artifacts/PHASE1_INVENTORY_ai_client.md")
+INV_RAG = Path("tests/artifacts/PHASE1_INVENTORY_rag_engine.md")
+
+MIG = {"INTERNAL_BROAD_CATCH", "INTERNAL_SILENT_SWALLOW", "INTERNAL_OPTIONAL_RETURN", "INTERNAL_RETHROW", "UNCLEAR"}
+EXPECTED = {
+    "src\\mcp_client.py": (40, 5, 0, 0, 1, 46),
+    "src\\ai_client.py": (17, 9, 0, 7, 0, 33),
+    "src\\rag_engine.py": (5, 1, 0, 3, 0, 9),
+}
+
+
+def test_phase1_audit_json_exists():
+    assert AUDIT_PATH.exists(), f"missing audit json at {AUDIT_PATH}"
+
+
+def test_phase1_inventory_docs_exist():
+    for p in [INV_MCP, INV_AI, INV_RAG]:
+        assert p.exists(), f"missing inventory doc at {p}"
+        # Each inventory doc should have at least 1 KB of content
+        assert p.stat().st_size > 500, f"inventory doc {p} too small"
+
+
+def test_phase1_total_migration_target_is_88():
+    data = json.loads(AUDIT_PATH.read_text(encoding="utf-8"))
+    files = {f["filename"]: f for f in data["files"]}
+    total = 0
+    for key in EXPECTED:
+        findings = files[key]["findings"]
+        mig = [f for f in findings if f["category"] in MIG]
+        total += len(mig)
+    assert total == 88, f"expected 88 migration-target sites, got {total}"
+
+
+def test_phase1_per_file_site_counts():
+    """mcp=46, ai=33, rag=9 = (BC, SS, OPT, RETHROW, UNCLEAR, total)"""
+    data = json.loads(AUDIT_PATH.read_text(encoding="utf-8"))
+    files = {f["filename"]: f for f in data["files"]}
+    for key, expected in EXPECTED.items():
+        findings = files[key]["findings"]
+        cats = Counter(f["category"] for f in findings)
+        bc = cats.get("INTERNAL_BROAD_CATCH", 0)
+        ss = cats.get("INTERNAL_SILENT_SWALLOW", 0)
+        opt = cats.get("INTERNAL_OPTIONAL_RETURN", 0)
+        rethrow = cats.get("INTERNAL_RETHROW", 0)
+        unclear = cats.get("UNCLEAR", 0)
+        mig = bc + ss + opt + rethrow + unclear
+        assert (bc, ss, opt, rethrow, unclear, mig) == expected, (
+            f"{key}: expected BC={expected[0]} SS={expected[1]} OPT={expected[2]} "
+            f"RETHROW={expected[3]} UNCLEAR={expected[4]} MIG={expected[5]}, "
+            f"got BC={bc} SS={ss} OPT={opt} RETHROW={rethrow} UNCLEAR={unclear} MIG={mig}"
+        )