fix(bigmind): apply 4 health-check fixes — BUG-1/2/3 + PERF-1

BUG-1: fix test_server_tools.py assert "ALWAYS" → "Always" (case mismatch)
BUG-2: export_memory() now includes hypotheses, upgrade_requests, token_saves,
        people tables; renamed bigmind_version → bigmind_schema_version (int)
BUG-3: auto_close.py replaced CURRENT_TIMESTAMP (SQLite) with Python
        datetime.now(timezone.utc).isoformat() for consistent UTC timestamps
PERF-1: context_builder.py caps get_facts() at _MAX_CONTEXT_FACTS=50 with
         overflow hint to prevent unbounded context growth

All 297 tests passing. Upgrade requests #6-9 resolved.
Health report: plans/BIGMIND_HEALTH_REPORT_2026-04-04.md

mcp/bigmind/tests/test_server_tools.py

@@ -541,7 +541,7 @@ class TestMemoryGetInstructions:
 
     def test_contains_mandatory_language(self, temp_db):
         result = memory_get_instructions()
-        assert "ALWAYS" in result
+        assert "Always" in result
 
 
 # ── memory_health_check ────────────────────────────────────────────────────────
@@ -674,7 +674,8 @@ class TestMemoryExport:
         memory_export(output_path=out)
         data = json.loads(Path(out).read_text())
         assert "export_date" in data
-        assert data["bigmind_version"] == "1.0"
+        assert "bigmind_schema_version" in data
+        assert isinstance(data["bigmind_schema_version"], int)
 
 
 # ── memory_deprecate_fact ──────────────────────────────────────────────────────