docs: bring home-screen widgets into M10, out of post-v1

Widgets share M10's machinery end to end: the next-alarm and timer
state a widget mirrors is exactly what the settings/backup/self-check
work already touches, and a widget tap is just another caller of the
MainActivity door the AlarmClock contract already opens. Keeping them
parked in post-v1 would mean building the same read paths twice.

QS tile, screensaver and bedtime stay deferred — none of them shares
M10's surface the way widgets do.

Also tightens PLAN.md §4's DND wording (interruption-filter read, no
ACCESS_NOTIFICATION_POLICY) and §7's backup semantics (whole-state
replace, ring state excluded, Room column vocabulary) ahead of M10's
implementation.

docs/ROADMAP.md

@@ -586,13 +586,16 @@ next-alarm publishing. Hostile-input validation at the intent boundary.
   hardware**, as no device was attached — the same caveat M5's seven, M6's four,
   M7's four and M8's four carry.
 
-### ⬜ M10 — Settings, backup, and the self-check
+### ⬜ M10 — Settings, backup, the self-check, and widgets
 - Settings composed from kit components: theme, dynamic colour, language,
   alarm/timer/clock defaults, about + crash reporting.
-- JSON backup export/import via SAF (`PLAN.md` §7), schema documented in the repo.
+- JSON backup export/import via SAF (`PLAN.md` §7), schema documented in
+  `docs/BACKUP.md`.
 - The **"why might my alarm not ring?"** self-check screen (`PLAN.md` §4) —
   real device state, deep links to the exact settings pages.
-- **Tests:** backup round-trip and unknown-field tolerance.
+- Three Glance home-screen widgets — next alarm, timer, clock (`PLAN.md` §9).
+- **Tests:** backup round-trip and unknown-field tolerance; self-check rule
+  logic per permission/state combination; widget model selection/formatting.
 
 ### ⬜ M11 — Release readiness
 Translations wired to Weblate, fastlane metadata and screenshots, F-Droid
@@ -608,7 +611,6 @@ Deferred deliberately, in rough priority order:
 
 - **Dock / screensaver mode** — a `DreamService` full-screen clock. Cheapest big
   win, and the surface people look at most.
-- **Glance home-screen widget** — next alarm and running timer.
 - **Quick Settings tile** — timer control and next alarm from the shade.
 - **Bedtime / sleep schedule** — wind-down and wake, with DND handoff. A feature
   in its own right, realistically v2.