Phase 36: add studio mixer channel strips and refresh screenshots

docs/ROADMAP.md

@@ -1013,6 +1013,31 @@ See [PREFERENCES.md](PREFERENCES.md) for configuration, workflow and limitations
 
 ---
 
+## Phase 36 — Studio Mixer Overview
+
+### Goal
+Show every track and bus as a studio-style channel strip with direct level,
+pan, routing and metering controls in the flat workspace.
+
+### Tasks and acceptance criteria
+- [x] Replace the single-track control panel with a horizontally scrolling bank of all tracks and buses.
+- [x] Provide vertical dB faders, flat pan knobs, mute/solo switches and output routing per strip.
+- [x] Show simultaneous stereo track/bus meters and keep the master output monitor visible while scrolling.
+- [x] Retain selected-track gain/pan automation, interpolation, keyboard control and Add bus.
+- [x] Preserve stable track identity, undo/redo, persistence and failure rollback across strip edits.
+- [x] Verify empty/full sessions, reorder/remove, minimum/large layouts and independent meters.
+- [x] Refresh the view screenshots and document mixer controls and metering limits.
+- [x] Build and run GUI/core, live JACK, sanitizer and release checks.
+
+### Implementation status
+Implemented in the C++ FLTK GUI using the existing C mixer and backend snapshot
+APIs. No audio callback, project format or dependency changes. The fixed master
+strip monitors graph output; it does not introduce a separate master gain stage.
+Faders edit static gain and do not chase automation. See [MIXER.md](MIXER.md)
+and the updated [screenshots](../screenshots/README.md).
+
+---
+
 ## Recommended Execution Order
 
 Reorder the phases when the audit reveals a blocking dependency. Do not mark a phase complete merely because code exists: its acceptance criteria must be demonstrated by builds, tests, or documented manual verification.