Phase 35: add persistent preferences and sequencer loop playback

docs/ROADMAP.md

@@ -989,6 +989,30 @@ patches control its audible response. See WORKSPACE.md and MIDI.md.
 
 ---
 
+## Phase 35 — Application Preferences and Sequencer Looping
+
+### Goal
+Persist application preferences in `~/.xtc.conf` and provide selectable sequencer loops.
+
+### Tasks and acceptance criteria
+- [x] Add a flat, tabbed Edit / Preferences dialog with Apply and Close.
+- [x] Validate and atomically save all preference tabs as a private INI file; load at startup.
+- [x] Expose audio, interface, editing, new-project, plugin-path and transport settings.
+- [x] List plugin files from configurable CLAP, VST2, VST3 and LADSPA search paths without executing modules.
+- [x] Select a snapped loop range by Shift-dragging the ruler or entering tick bounds.
+- [x] Toggle looping and split audio processing at exact sample boundaries.
+- [x] Preserve real-time constraints and reject recording with looping enabled.
+- [x] Verify persistence, invalid input, GUI Apply/reload, backend wraps and existing regressions.
+
+### Implementation status
+Implemented without dependencies or a project format change. Application settings
+are saved only with Apply; audio connection options take effect on Reconnect and
+project defaults on New. Existing projects retain their musical data. Loop ranges
+are global preferences, not project data. Enabled loops require at least 64 samples.
+See [PREFERENCES.md](PREFERENCES.md) for configuration, workflow and limitations.
+
+---
+
 ## 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.