docs(bf-4bhb7): document RUST_LOG unset state

notes/bf-3bnao-step1.md

@@ -0,0 +1,26 @@
+# bf-3bnao-step1: Verify RUST_LOG is unset
+
+## State: PASS
+
+**Date:** 2026-07-06
+
+## Verification
+
+Checked RUST_LOG environment variable state:
+
+```bash
+echo "RUST_LOG current value: '$RUST_LOG'"
+# Output: RUST_LOG current value: ''
+```
+
+## Result
+
+- RUST_LOG is **unset** (empty string)
+- No action required
+- Ready to proceed to next step
+
+## Acceptance Criteria
+
+- ✅ Run `echo $RUST_LOG` and verify output is empty - **PASS**
+- ✅ If RUST_LOG is set, run `unset RUST_LOG` and verify it is now unset - **N/A** (already unset)
+- ✅ Document the state in notes/bf-3bnao-step1.md - **PASS**