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>

app/src/test/java/de/jeanlucmakiola/floret/data/tasks/TaskWriteMapperTest.kt

@@ -28,6 +28,50 @@ class TaskWriteMapperTest {
         assertThat(values[Tasks.TZ]).isEqualTo("Europe/Berlin")
     }
 
+    @Test
+    fun `percent complete is written and clamped to 0-100`() {
+        val values = TaskWriteMapper.taskValues(
+            TaskForm(title = "x", listId = 1L, percentComplete = 140),
+            tzId = "UTC",
+        )
+        assertThat(values[Tasks.PERCENT_COMPLETE]).isEqualTo(100)
+
+        val unset = TaskWriteMapper.taskValues(TaskForm(title = "x", listId = 1L), tzId = "UTC")
+        assertThat(unset[Tasks.PERCENT_COMPLETE]).isNull()
+    }
+
+    @Test
+    fun `progress keeps completion in sync both ways`() {
+        // 100% completes the task (timestamp left to the provider / existing value).
+        val done = TaskWriteMapper.taskValues(
+            TaskForm(title = "x", listId = 1L, percentComplete = 100),
+            tzId = "UTC",
+        )
+        assertThat(done[Tasks.STATUS]).isEqualTo(TasksContract.STATUS_COMPLETED)
+        assertThat(done.containsKey(Tasks.COMPLETED)).isFalse()
+
+        // Below 100% reopens it and clears the completion timestamp.
+        val reopened = TaskWriteMapper.taskValues(
+            TaskForm(title = "x", listId = 1L, percentComplete = 75),
+            tzId = "UTC",
+        )
+        assertThat(reopened[Tasks.STATUS]).isEqualTo(TasksContract.STATUS_IN_PROCESS)
+        assertThat(reopened[Tasks.COMPLETED]).isNull()
+
+        // No percent in the form ⇒ status is left to the complete toggle.
+        val untouched = TaskWriteMapper.taskValues(TaskForm(title = "x", listId = 1L), tzId = "UTC")
+        assertThat(untouched.containsKey(Tasks.STATUS)).isFalse()
+    }
+
+    @Test
+    fun `parent id is written so a task can be filed under another`() {
+        val values = TaskWriteMapper.taskValues(
+            TaskForm(title = "x", listId = 1L, parentId = 7L),
+            tzId = "UTC",
+        )
+        assertThat(values[Tasks.PARENT_ID]).isEqualTo(7L)
+    }
+
     @Test
     fun `all-day task clears the timezone`() {
         val form = TaskForm(

app/src/test/java/de/jeanlucmakiola/floret/domain/TaskFormTest.kt

@@ -35,4 +35,13 @@ class TaskFormTest {
         val errors = TaskForm(title = "x", listId = 1, reminderMinutesBeforeDue = 10).validate()
         assertThat(errors).contains(TaskFormError.REMINDER_WITHOUT_DUE)
     }
+
+    @Test
+    fun `progress and parent auto-reveal only when they carry a value`() {
+        assertThat(TaskForm(title = "x", listId = 1).populatedFields()).isEmpty()
+        assertThat(TaskForm(title = "x", listId = 1, percentComplete = 0, parentId = 0).populatedFields())
+            .isEmpty()
+        assertThat(TaskForm(title = "x", listId = 1, percentComplete = 30, parentId = 9).populatedFields())
+            .containsExactly(TaskFormField.Progress, TaskFormField.Parent)
+    }
 }