Phase 4: Add modular graph editor and transactional graph edits

tests/integration/README.md

@@ -63,3 +63,28 @@ CFLAGS/CXXFLAGS and LDFLAGS, using the baseline warning/include/standard flags
 from BUILD.md. Keep FLTK's `-I` and `-D` flags from `fltk-config --cxxflags`,
 but exclude the distribution's GCC-specific LTO/object-code flags for Clang.
 No suppressions are used for core/backend/realtime sanitizer tests.
+
+## Phase 4 graph editing coverage
+
+The same `make test-gui` target now adds nodes through toolbar callbacks,
+connects the exact rendered graph, validates expected oscillator/gain samples
+in the submitted backend plan, checks cycle/direction/duplicate rejection,
+checks backend I/O/pending-capacity rollback, deletes wires and incident edges,
+and verifies stable IDs, preserved positions, prepared/queued/active feedback
+and empty-graph silence. The fake backend compiles submitted C snapshots rather
+than accepting an unrelated GUI model. Move-only actions do not submit plans.
+
+`make test-gui-jack` exercises the same widget against real JACK: it builds a
+graph while stopped, starts it, adds/deletes nodes during active processing,
+waits for revision acknowledgement, and rejects cycles without changing the
+model. Start/stop/reconnect and callback-safe active close remain covered. No
+routes are created by this test. Core tests separately check known sample
+changes after deleting/reconnecting nodes and meter lookup after ID compaction.
+
+A live xdotool mouse run under a 1280x800 Xvfb display created oscillator → gain
+→ meter → output by dragging ports, observed a rejected feedback cycle, moved
+a source with its wire attached, deleted a wire and node, and closed while
+running. Visual inspection confirmed actual wires and active-state feedback,
+with zero xruns reported during that smoke run. Zoom, multiselection, editable
+parameters, project save/load, realtime meter visualization and hardware routing
+controls are outside this phase. Node layout currently lasts only for a session.