feat: plan modern editing phases and add arrangement multi-selection

docs/ROADMAP.md

@@ -1312,6 +1312,171 @@ BUILTIN_DEVICES.md. Application project format is now 15, reading versions 1–1
 
 ---
 
+## Phase 47 — Arrangement Multi-selection
+
+### Goal
+Select clips across tracks with additive selection and Select all; preserve stable IDs across refresh and docking.
+
+### Tasks and acceptance criteria
+- [x] Provide the control/model behavior and accessible GUI commands.
+- [x] Validate bounds and failure rollback; preserve existing project compatibility and callback safety.
+- [x] Test the new workflow and document scope and limitations.
+
+### Implementation status
+Implemented: additive Shift-click selection, Ctrl+A/Select all and selected clip outlines across tracks. Stable IDs survive refresh and panel reparenting. Core build/tests and GUI selection/docking tests pass.
+
+---
+
+## Phase 48 — Transactional Group Editing
+
+### Goal
+Move, duplicate and delete selected clips atomically, preserving relative positions and a single undo step.
+
+### Tasks and acceptance criteria
+- [ ] Provide the control/model behavior and accessible GUI commands.
+- [ ] Validate bounds and failure rollback; preserve existing project compatibility and callback safety.
+- [ ] Test the new workflow and document scope and limitations.
+
+### Implementation status
+Planned.
+
+---
+
+## Phase 49 — Arrangement Clipboard
+
+### Goal
+Copy selected clips into an independent session clipboard and paste at the cursor with fresh IDs, notes and media references.
+
+### Tasks and acceptance criteria
+- [ ] Provide the control/model behavior and accessible GUI commands.
+- [ ] Validate bounds and failure rollback; preserve existing project compatibility and callback safety.
+- [ ] Test the new workflow and document scope and limitations.
+
+### Implementation status
+Planned.
+
+---
+
+## Phase 50 — Repeat Arrangement Patterns
+
+### Goal
+Repeat a selected phrase by its complete bounding span with bounded copy counts and all-or-nothing capacity validation.
+
+### Tasks and acceptance criteria
+- [ ] Provide the control/model behavior and accessible GUI commands.
+- [ ] Validate bounds and failure rollback; preserve existing project compatibility and callback safety.
+- [ ] Test the new workflow and document scope and limitations.
+
+### Implementation status
+Planned.
+
+---
+
+## Phase 51 — Align and Slip Editing
+
+### Goal
+Align selected clip starts to the cursor and slip source offsets without moving timeline boundaries.
+
+### Tasks and acceptance criteria
+- [ ] Provide the control/model behavior and accessible GUI commands.
+- [ ] Validate bounds and failure rollback; preserve existing project compatibility and callback safety.
+- [ ] Test the new workflow and document scope and limitations.
+
+### Implementation status
+Planned.
+
+---
+
+## Phase 52 — MIDI Swing Quantization
+
+### Goal
+Apply bounded swing and quantize strength to source note starts with deterministic rounding and source-bound checks.
+
+### Tasks and acceptance criteria
+- [ ] Provide the control/model behavior and accessible GUI commands.
+- [ ] Validate bounds and failure rollback; preserve existing project compatibility and callback safety.
+- [ ] Test the new workflow and document scope and limitations.
+
+### Implementation status
+Planned.
+
+---
+
+## Phase 53 — MIDI Legato and Gate Tools
+
+### Goal
+Set note gates or extend notes to the next onset on the same channel, preserving IDs and validating all notes before publication.
+
+### Tasks and acceptance criteria
+- [ ] Provide the control/model behavior and accessible GUI commands.
+- [ ] Validate bounds and failure rollback; preserve existing project compatibility and callback safety.
+- [ ] Test the new workflow and document scope and limitations.
+
+### Implementation status
+Planned.
+
+---
+
+## Phase 54 — MIDI Scale Correction
+
+### Goal
+Snap notes to a chosen root and chromatic, major or minor scale with deterministic nearest-pitch ties.
+
+### Tasks and acceptance criteria
+- [ ] Provide the control/model behavior and accessible GUI commands.
+- [ ] Validate bounds and failure rollback; preserve existing project compatibility and callback safety.
+- [ ] Test the new workflow and document scope and limitations.
+
+### Implementation status
+Planned.
+
+---
+
+## Phase 55 — MIDI Velocity Shaping
+
+### Goal
+Apply bounded velocity scaling and offsets to selected MIDI clips, with explicit clipping to valid MIDI velocities.
+
+### Tasks and acceptance criteria
+- [ ] Provide the control/model behavior and accessible GUI commands.
+- [ ] Validate bounds and failure rollback; preserve existing project compatibility and callback safety.
+- [ ] Test the new workflow and document scope and limitations.
+
+### Implementation status
+Planned.
+
+---
+
+## Phase 56 — Batch Audio Fade Tools
+
+### Goal
+Apply symmetric boundary fades or remove fades on selected audio clips, preserving clip gain, media and timing.
+
+### Tasks and acceptance criteria
+- [ ] Provide the control/model behavior and accessible GUI commands.
+- [ ] Validate bounds and failure rollback; preserve existing project compatibility and callback safety.
+- [ ] Test the new workflow and document scope and limitations.
+
+### Implementation status
+Planned.
+
+---
+
+## Phase 57 — Mixer A/B Comparison
+
+### Goal
+Capture and recall two session mixer snapshots by stable track ID, with transactional validation, undo and explicit automation limitations.
+
+### Tasks and acceptance criteria
+- [ ] Provide the control/model behavior and accessible GUI commands.
+- [ ] Validate bounds and failure rollback; preserve existing project compatibility and callback safety.
+- [ ] Test the new workflow and document scope and limitations.
+
+### Implementation status
+Planned.
+
+---
+
 ## 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.