feat: dock editor panels and add resizable pinned track headers

docs/BUILTIN_DEVICES.md

@@ -23,9 +23,9 @@ Changes use the existing stopped-engine preparation and undo workflow.
 
 These are basic mono processors; stereo plans use independent instances. Reverb
 is deliberately simple and has no room model or stereo diffusion. Delay time
-changes can click; there is no crossfade or tempo sync. Transport seeks retain
-existing effect history, like LADSPA. Effect tails require continued rendering;
-playback/export does not automatically extend the song for tails.
+changes can click; these original devices have no crossfade or tempo sync.
+Internal effect history resets on transport discontinuities. Phase 44 below
+documents configurable export tails and optional playback stopping after tails.
 
 Project format 13 stores internal devices as format 4 with reserved module path
 `/xtc/internal`, stable numeric identity and index (0 keys, 1 bass, 2 delay,

docs/PREFERENCES.md

@@ -76,3 +76,9 @@ Phase 45 adds `[interface] transport_detached`, `mixer_detached`, and each
 panel's `_x`, `_y`, `_width`, `_height` rectangle. Use Preferences / Apply after
 moving panels to save the captured layout. Restoration clamps rectangles to the
 current display; the floating transport wraps at narrow widths.
+
+Phase 46 extends `[interface]` with `sequencer_detached`, `graph_detached`,
+`piano_detached`, editor window geometry and `track_header_width` (180..360).
+Piano retains `piano_width`/`piano_height` and adds `piano_x`/`piano_y`.
+Reset workspace layout changes the session; Preferences / Apply persists it.
+Only original-tab docking and floating windows are supported.

docs/ROADMAP.md

@@ -1065,9 +1065,9 @@ track in other views. Command search lists active menu actions; it is not a
 plugin scanner or a key-binding editor. See WORKSPACE.md.
 
 ### Future usability work
-Dockable editor panels, arrangement multiselection, independent track inserts,
-resizable pinned track headers and customizable shortcuts remain future work.
-They require separate model/layout designs and acceptance tests.
+Arrangement multiselection, independent track inserts and customizable shortcuts
+remain future work. Dockable editor panels and resizable pinned track headers
+are implemented in Phase 46.
 
 ---
 
@@ -1099,10 +1099,9 @@ keys/delay project round trip. Shared GUI tests cover instrument selection,
 history and plugin editing, but do not constitute a dedicated end-to-end matrix
 for all four internal devices. Additional qualification is tracked in Phase 40.
 
-Missing extensions: editable instrument parameters/presets, pitch bend, sample
-instruments, click-free/tempo-synced delay, stereo reverb/diffusion, explicit seek
-history policy and automatic tail rendering. These are planned in Phases 41–44;
-they are not part of the checked initial subset. See
+The initial subset lacked editable presets, pitch bend, sample instruments,
+smooth/tempo-synced delay, stereo reverb, seek history policy and automatic tails.
+These audit gaps are addressed by Phases 41–44 below. See
 [BUILTIN_DEVICES.md](BUILTIN_DEVICES.md) for controls and explicit limitations.
 
 ---
@@ -1128,10 +1127,9 @@ detach/dock, close-to-dock, shared BPM/loop state, floating playback shortcuts,
 main/floating resizing and failed/successful shutdown. Floating screenshots are
 listed in [screenshots/README.md](../screenshots/README.md).
 
-Layout and window positions are session-only. The floating transport requires
-1220 pixels of width; mixer minimum size is 600 × 420. Other editors cannot be
-detached, and general dock layouts are absent. Persistence, compact transport
-and additional panels are tracked in Phases 45–46. See
+The original subset used session-only positions, a 1220-pixel transport and
+only two detachable panels. Phases 45–46 add persisted geometry, a compact
+transport and editor panels. Mixer minimum remains 600 × 420. See
 [WORKSPACE.md](WORKSPACE.md) for usage and limits.
 
 ### Audit validation (Phases 38–39)
@@ -1282,17 +1280,35 @@ The full-window minimum is unchanged. See WORKSPACE.md and PREFERENCES.md.
 Extend Phase 39's two-panel arrangement to a general editor workspace.
 
 ### Tasks and acceptance criteria
-- [ ] Define supported dock locations and layout ownership for sequencer, piano roll and modular graph panels.
-- [ ] Detach/dock each supported editor without duplicating project, selection or history state.
-- [ ] Support resizable pinned track headers and preserve editing coordinates, scrolling and focus after reparenting.
-- [ ] Integrate with Phase 45 layout persistence and provide a safe reset-layout action.
-- [ ] Verify minimum/large layouts, cross-panel editing, repeated reparenting and shutdown/error paths.
+- [x] Define supported dock locations and layout ownership for sequencer, piano roll and modular graph panels.
+- [x] Detach/dock each supported editor without duplicating project, selection or history state.
+- [x] Support resizable pinned track headers and preserve editing coordinates, scrolling and focus after reparenting.
+- [x] Integrate with Phase 45 layout persistence and provide a safe reset-layout action.
+- [x] Verify minimum/large layouts, cross-panel editing, repeated reparenting and shutdown/error paths.
 
 ### Implementation status
-Planned. Phase 39 only detaches transport and mixer; broader docking and
-resizable pinned headers from Phase 37 remain outstanding. These follow-up
-phases cover gaps found in Phases 38–39 and their documented limitations;
-unrelated outstanding features in earlier phases retain their existing status.
+Implemented: complete Sequencer/Graph panels and Piano Roll reparent between
+floating windows and their main tabs, with shared model/history/selection and
+preserved scroll positions. Validated preferences persist layouts; reset docks
+panels and restores default rectangles. Arrangement headers/selectors stay pinned
+and resize from 180 to 360 pixels. Supported docking is explicitly limited to
+original tabs; arbitrary split layouts and drag docking are future extensions.
+Core/settings, GUI lifecycle/editing/restart and integrated checks are recorded
+below. See WORKSPACE.md and PREFERENCES.md.
+
+---
+
+### Integrated validation for Phases 40–46
+
+Each phase was built and tested before its separate implementation commit.
+Core/reliability tests cover devices, migration, persistence, DSP partitions,
+transport history and export. GUI tests cover editing, shared state and panel
+lifecycle; CLAP/VST2/VST3/LADSPA fixture and live software JACK suites retain the
+existing workflows. Sanitizers cover built-in DSP/export and GUI lifetimes;
+static analysis and staged installation check the final integrated changes.
+Human listening, arbitrary third-party plugins and physical hardware remain
+unqualified. Listening WAV generation and manual procedures are documented in
+BUILTIN_DEVICES.md. Application project format is now 15, reading versions 1–14.
 
 ---
 

docs/WORKSPACE.md

@@ -169,9 +169,10 @@ Space and menu playback shortcuts work from either floating panel, with normal
 numeric/text editing protection. Closing the main window closes all panels only
 after the existing unsaved/recording/backend shutdown checks succeed.
 
-Window detachment and positions are session-only; startup uses the docked layout.
-The floating transport is a wide toolbar (minimum 1220 pixels); the floating
-mixer resizes down to 600 × 420 and retains horizontal track scrolling.
+The initial Phase 39 layout used session-only positions and a transport minimum
+width of 1220 pixels. Phase 45 below adds saved layouts and transport wrapping
+down to 400 pixels. The floating mixer resizes down to 600 × 420 and retains
+horizontal track scrolling.
 
 Verified with `make BUILD_DIR=build/phase39 gui test-gui test-gui-instruments
  test-gui-jack` (one line), plus the GUI suite under AddressSanitizer/UBSan.
@@ -193,3 +194,39 @@ the wide toolbar and arrangement geometry. Mixer minimum remains 600 × 420.
 Existing close-to-dock, Dock all and shortcuts retain their shared widget state.
 Tests cover narrow control bounds, save/restart, off-screen restoration, invalid
 geometry, repeated docking/resizing and shared transport state.
+
+## Phase 46 editor panels and pinned track headers
+
+**View → Detach sequencer** and **Detach modular graph** float each complete
+editor, including its toolbar and scroll area. Its main tab offers Show and Dock
+buttons. Closing the floating window docks it; View shortcuts also raise floating
+editors. Supported dock locations are their original main-window tabs; arbitrary
+split regions, tab reordering and drag-to-dock are not implemented. Sequencer
+minimum floating size is 1100 × 420; Graph is 1000 × 420.
+
+The Piano roll now also has a main-window tab. Select a MIDI clip and open it as
+before. **View → Float piano roll** switches its existing widgets between the tab
+and a floating window; closing the floating window docks it. The tab's Open
+selected MIDI clip button opens the current selection. Default floating behavior
+is retained for older preferences. A missing/invalid MIDI selection is reported.
+All panels share project/history, preserve editor selections and scroll offsets,
+and retain playback shortcuts and text-input protection.
+
+**View → Dock all panels** includes all editors. **Reset workspace layout** docks
+all panels, restores default floating rectangles and resets header width. Use
+Preferences / Apply to persist either result. Editor dock state, floating window
+rectangles and header width use the same validated settings/restore path as the
+transport/mixer. Piano content opens lazily for the selected MIDI clip; startup
+does not invent a clip or save a project-specific selection in application settings.
+
+Arrangement track headers and instrument selectors now stay pinned during
+horizontal scrolling. Drag the divider within the header's final five pixels to
+resize from 180 to 360 pixels; Escape cancels the drag. Clip timing coordinates,
+snap and horizontal scrolling use the resized origin. Header layout is a UI
+preference, not an undoable project edit. Vertical scrolling remains shared with
+the track rows. Clips covered by the pinned header cannot be selected through it.
+
+GUI regressions cover repeated detach/dock and close-to-dock, toolbar ownership,
+minimum/large resize, shared model/note/clip selection, scrolling, header dragging,
+short-clip hit tests, Apply/restart, reset layout and failed/successful shutdown.
+ASan/UBSan checks retain only the existing system Fontconfig leak suppression.