M4: percent-complete, conflict-safe saves & subtask reparent

M3 detail/edit polish:
- "Progress" slider on the edit form writes Tasks.PERCENT_COMPLETE (clamped
  0-100, 5% detents); status stays owned by the complete toggle.
- Conflict-safe saves: updateTask re-checks the provider's last_modified against
  the value captured when the form loaded and throws TaskConflictException; the
  editor offers overwrite-or-cancel instead of clobbering an external change.

M4 subtasks (UI):
- Reparent: a "Parent task" picker files a task under any top-level task in its
  list (or "None" to promote it); candidates stay top-level to keep nesting one
  level deep. Switching list clears the now-invalid parent.
- Tapping a subtask opens its own detail (a new TaskDetail entry, own VM).

Tests: percent clamping, parent-id write, populatedFields reveal logic.
Docs: ROADMAP M2/M3/M4 reconciled to the codebase; CHANGELOG [Unreleased].

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

docs/ROADMAP.md

@@ -11,9 +11,12 @@ Status legend: ✅ done · 🚧 in progress · ⬜ not started
 ## Current state (one line)
 
 The full non-visual stack ("backoffice") over the OpenTasks `TaskContract`
-provider is **done and unit-tested**; the Material 3 Expressive UI is being
-built screen by screen on top of it. App builds, gates on provider/permission,
-and navigates lists → task list → detail / edit through base screen scaffolds.
+provider is **done and unit-tested**, and the Material 3 Expressive UI is built
+through **M4**: lists → task list (swipe gestures, inline add, smart-list section
+headers) → detail / edit with full CRUD, date-time pickers, priority,
+percent-complete, conflict-safe saves, per-task reminders, and subtask
+create + reparent. Remaining work is M5 (notification / exact-alarm onboarding,
+default reminder UI) and M6 (Settings screen, Glance widget, i18n, release).
 
 ---
 
@@ -39,38 +42,81 @@ The complete non-visual stack:
 - JVM unit tests across mappers, filtering, sorting, form, value mapping, and
   day windows.
 
-### 🚧 M2 — Screens: lists, task list, complete & CRUD
-Replace the functional scaffold with the real Material 3 Expressive UI, screen
-by screen, against the already-built ViewModels.
+### ✅ M2 — Screens: lists, task list, complete & CRUD
+The real Material 3 Expressive UI, built screen by screen against the M1
+ViewModels.
 - ✅ Provider/permission onboarding gate (`RootScreen`).
 - ✅ Lists overview (`ListsScreen`) — smart lists + user lists grouped by account.
 - ✅ Navigation host wiring (`FloretNavHost` + `Dest` route table: lists → task
   list → detail / edit, each binding its M1 ViewModel from route args).
-- 🚧 Task list screen — base scaffold lands (checkbox rows, toggle-complete, open
-  / new-task nav). Remaining: swipe-to-complete / -delete, inline add field,
-  section headers for smart lists.
-- 🚧 Detail + edit screens — base scaffolds land (detail shows title /
-  description / subtasks with edit+delete; edit has title / description / save).
-  Remaining: full CRUD fields and local-list creation wired to the UI.
+- ✅ Task list screen — checkbox rows + toggle-complete, swipe-to-complete /
+  -delete (`SwipeToDismissBox`), inline add field (`InlineAdd` → `quickAdd`),
+  smart-list section headers (`TaskSections`).
+- ✅ Detail + edit screens — detail shows title / description / subtasks with
+  edit+delete; edit has the full CRUD form (title, description, save) wired to a
+  list picker.
 
-### ⬜ M3 — Detail / edit polish
-Task detail and edit screens: due/start date-time pickers, priority,
-percent-complete, conflict-safe saves (re-check before overwrite), smart-list
-section presentation.
+### ✅ M3 — Detail / edit polish
+- ✅ Due / start date-time pickers (`DateTimePickerFlow` in `TaskEditScreen`).
+- ✅ Priority — coloured by level: green / amber / red pastels (`priorityFill`;
+  M3 has no priority role, only `error`). A shared `ui/common/PriorityChip` on the
+  list and detail screens, and the edit form's M3 segmented selector tints its
+  active segment in the chosen level's hue.
+- ✅ Smart-list section presentation (`TaskSections` headers on the task list).
+- ✅ Percent-complete field — optional "Progress" slider (5% detents) on the edit
+  form; writes `Tasks.PERCENT_COMPLETE` (clamped 0–100, status left to the
+  complete toggle).
+- ✅ Conflict-safe saves — `updateTask` re-checks `last_modified` against the
+  value captured when the form loaded and throws `TaskConflictException`; the
+  editor offers overwrite-or-cancel instead of clobbering an external change.
 
-### ⬜ M4 — Subtasks (UI)
-`RELATED-TO` hierarchy in the UI: indentation, create subtask, reparent. The
-data layer already reads `parentId`; this is the trickiest UI piece.
+### ✅ M4 — Subtasks (UI)
+`RELATED-TO` hierarchy in the UI. The data layer already reads `parentId`.
+- ✅ Create subtask (`AddSubtaskField` → `TaskDetailViewModel.addSubtask` sets
+  `parentId`); subtasks render as a grouped section in the detail screen. Tapping
+  a subtask opens its own detail (a new `TaskDetail` entry, so it can have
+  children too), and the subtask's detail shows a tappable "Part of …" parent
+  card so it never reads as a stray standalone task.
+- ✅ Inline expansion on the task list — a parent row has a dedicated expand
+  button (trailing chevron, separate from the count chip). Each section flattens
+  into one grouped run (parents + their expanded children) and corners are chosen
+  per-edge (`cornerPosition`): top-level tasks keep their own run, an expanded
+  parent opens its bottom to its children, and the child group rounds off on its
+  last segment while the next top-level task stays mid-run. Children are
+  full-width, set a step down in tone (`surfaceContainer` vs the parents'
+  `surfaceContainerHigh`) and with no colour bar (checkbox stays aligned). An expanded group ends with an inline "add a subtask"
+  row (always on for now; an opt-out toggle lands with the M6 settings screen).
+  Offered only where the list holds all the children (a real list; smart lists
+  that omit off-day children stay collapsed). `TaskDetail.parent` carries the
+  parent for the detail card.
+- ✅ Reparent — a full-width, searchable "Parent task" sheet on the edit form
+  groups active candidates by due-date section (Overdue / Today / Upcoming / No
+  date) and files a task under any top-level task in its list (or "None" to
+  promote it); switching list clears the now-invalid parent. Candidates stay
+  active + top-level to keep nesting one level deep, matching the detail screen.
 
-### ⬜ M5 — Reminders onboarding & polish
-The engine exists (M1). Remaining: the `POST_NOTIFICATIONS` + exact-alarm
-onboarding flow, per-task / default reminder-offset settings UI, and
-end-to-end verification on device.
+### 🚧 M5 — Reminders onboarding & polish
+The engine exists (M1: `ReminderScheduler` + boot / provider-change re-sync,
+`DueReminderReceiver`, `TaskNotifier`).
+- ✅ Per-task reminder-offset UI (`ReminderPickerDialog` → `TaskForm`
+  `reminderMinutesBeforeDue`).
+- ⬜ `POST_NOTIFICATIONS` + exact-alarm onboarding flow — currently only graceful
+  runtime checks (`TaskNotifier.canPost`, `canScheduleExactAlarms`), no
+  user-facing gate.
+- ⬜ Default reminder-offset settings UI — `SettingsPrefs`/`SettingsViewModel`
+  back it, but no Composable exposes it.
+- ⬜ End-to-end verification on device.
 
-### ⬜ M6 — Settings, widget, i18n, release
-Settings screen (theme / dynamic-color / language, default list, default
-reminder), Glance task-list widget, translations, finalize F-Droid metadata,
-confirm CI release flow.
+### 🚧 M6 — Settings, widget, i18n, release
+- ✅ F-Droid metadata scaffolded (`fdroid-metadata/`).
+- ⬜ Settings screen — `SettingsViewModel` exists but no `SettingsScreen`
+  Composable and it is not in the nav graph (only used by `MainActivity` for
+  app-level theming). Needs theme / dynamic-color / language, default list,
+  default reminder, and the opt-out toggle for the task list's inline
+  add-a-subtask row (on by default since M4).
+- ⬜ Glance task-list widget — deps present in `build.gradle.kts`, zero impl.
+- ⬜ Translations — only `res/values/` (English); no `values-XX`.
+- ⬜ Finalize F-Droid metadata, confirm CI release flow.
 
 ### ⬜ Posture B (separate track, later)
 Add a `:provider` module bundling the Apache-2.0 `opentasks-provider`;