Phase 23: refine routing inspection, signal-flow layout and atomic wire insertion

docs/ROADMAP.md

@@ -554,6 +554,23 @@ Preserve the modular spirit of the application while making complex projects und
 - Graph updates follow the documented real-time synchronization strategy.
 - GUI routing concepts map cleanly to the public C engine API.
 
+Implemented: cached public C routing analysis (edge counts, longest-path levels,
+output reachability and external-input fallback); directional/highlighted wires,
+role colors/labels, no-output badges, selection inspection and keyboard navigation;
+scrollable signal-flow auto-layout and non-overlapping initial placement. Atomic
+unity-gain wire insertion is one undoable C edit using existing node persistence.
+Core and mock/live GUI tests cover rollback, complete plan adoption, cycles,
+disconnect/restore and undo/redo. See ROUTING.md. Flat tracks/shared audio/MIDI
+sources do not yet represent folders or per-track routing templates; these
+conditional tasks are deferred. No format change, feedback processing, latency
+compensation or physical listening qualification is claimed.
+
+Acceptance evidence:
+- [x] Direction/role labels, layout and public routing diagnostics expose paths.
+- [x] Invalid/capacity/backend-failed commands retain the previous graph/plan.
+- [x] Live JACK graph tests verify complete block-boundary plan adoption.
+- [x] GUI routing analysis and edits use public C APIs; callback ownership is unchanged.
+
 ## Phase 24 — Mixing and Mastering Essentials
 
 ### Goal