feat(notecard): Re-entrant run_operation chokepoint + request-lock seam

All Notecard entry points funnel through run_operation(), which holds an optional operation lock for the whole operation; nested entry points (e.g. execute(const T&) inside execute(T&)) re-enter as no-ops via a depth counter. The operation lock reuses the IBusLock seam (set_request_lock/clear_request_lock); null default = zero behavioral cost. RTX/readiness is wired in a later task.

Author: m-mcgowan

ci.sh

@@ -196,7 +196,8 @@ NFEOF
         "$ROOT/tests/test_posix_serial.cpp" \
         "$ROOT/tests/test_notecard_move_semantics.cpp" \
         "$ROOT/tests/test_struct_sink_strings.cpp" \
-        "$ROOT/tests/test_bus_lock.cpp"
+        "$ROOT/tests/test_bus_lock.cpp" \
+        "$ROOT/tests/test_operation_lock.cpp"
     /tmp/note-cpp-tests
     echo "  tests: OK"
 

cmake/note-cpp-sources.cmake

@@ -158,6 +158,7 @@ set(NOTE_CPP_TEST_SOURCES_FULL_ONLY
     test_transport_timing.cpp
     test_layered_transport.cpp
     test_txn_handshake.cpp
+    test_operation_lock.cpp
     test_wire_format.cpp
     test_wire_format_jsonb.cpp
 )
@@ -194,6 +195,7 @@ set(NOTE_CPP_TEST_SOURCES_JSON_WIRE
     test_transport_serial.cpp
     test_transport_streaming.cpp
     test_txn_handshake.cpp
+    test_operation_lock.cpp
     test_wire_format.cpp
 )