Merge FB-03: grid-snapped HUD widgets with auto-fit text

# Conflicts:
#	docs/feedback/FB-03-grid-snapped-hud-widgets.md
#	lib/src/ui/record/record_screen.dart

docs/feedback/FB-03-grid-snapped-hud-widgets.md

@@ -1,6 +1,6 @@
 # FB-03 — Grid-snapped HUD widgets with auto-fit, centered text
 
-**Depends on** — · **Size** L · **Status** Not started
+**Depends on** — · **Size** L · **Status** Done
 
 ## Goal
 Rework the customizable HUD telemetry widgets (built in UI-04) from free-form fractional
@@ -601,3 +601,61 @@ FB-02 (hiding the idle Speed panel — separate ticket, this one only touches th
 recording-state HUD widgets themselves). Making widget text grow to actually fill a
 larger grid span (see Risks). Any change to which metrics exist or their default
 visibility set — `HudMetric`'s own enum and `label`s are untouched.
+
+## Outcome
+Implemented exactly per the Design section above, no deviations from the approach:
+
+- `lib/src/hud/hud_widget_layout.dart` rewritten with the 4x8 int grid
+  (`hudGridColumns`/`hudGridRows`), `col`/`row`/`colSpan`/`rowSpan` fields,
+  `clampedToGrid()`, top-level `hudRectsOverlap()`, updated `toJson`/`fromJson` (now
+  reading `col`/`row`/`colSpan`/`rowSpan` — an old `x`/`y`/`width`/`height` blob throws
+  in the try/catch and falls back to `defaultFor`, no migration code needed, as
+  predicted), an unchanged-in-spirit `defaultFor`, and the new `nextFreeSlot` scan.
+- `lib/src/hud/hud_layout_controller.dart` rewritten: `updatePosition`/`updateSize`
+  take ints, clamp, and reject-on-collision (no-op, no revert needed since state is
+  never mutated until the candidate passes); `setVisible` calls `nextFreeSlot` only
+  when the metric's own slot now collides with another visible widget.
+- `lib/src/ui/components/draggable_resizable_hud_widget.dart` rewritten: local
+  `_dragOffset`/`_resizeDelta` pixel state tracks the live gesture smoothly; snapping
+  to the nearest grid cell and calling `onMoved`/`onResized` exactly once happens on
+  `onLongPressEnd`/`onPanEnd`. Both offsets reset to zero right after that call
+  regardless of whether the controller accepted the move, which is what makes a
+  rejected move/resize visually snap back with no separate accept/reject callback.
+  Callback signatures changed to `void Function(int, int)`.
+- `lib/src/ui/components/hud_edit_overlay.dart`: the two callback closures updated to
+  the new int signatures; no other change needed.
+- `lib/src/ui/record/record_screen.dart`'s `_HudMetricValue.build()`: wrapped in
+  `FittedBox(fit: BoxFit.scaleDown)`, `maxLines`/`overflow` dropped from both `Text`s.
+
+**Confirmed trade-off** (the one the ticket flagged in advance): `BoxFit.scaleDown`
+never enlarges past the reference size, so a widget resized to `hudMaxColSpan` x
+`hudMaxRowSpan` renders the same 10px/18px text as a 1x1 widget — just with more empty
+space around it, still centered via `DraggableResizableHudWidget`'s existing
+`Center`. Verified directly with the new "largest allowed size" widget test (a 4x3
+`DraggableResizableHudWidget` at 400x400 pixels records no overflow exception, same as
+the 1x1 case) — text-scaling-with-widget-size remains explicit future work, not a
+silent gap.
+
+**Confirmed migration behavior**: an old-shaped saved layout (pre-this-ticket JSON with
+`x`/`y`/`width`/`height` keys) loads without crashing and falls back to `defaultFor`
+per metric — covered directly by a new `hud_widget_layout_test.dart` case and a new
+`config_test.dart` case using literal old-shaped JSON. No user-facing warning was
+added, per the ticket's own Risks section (no real user base yet to protect).
+
+**Tests**: `test/hud_widget_layout_test.dart` and `test/hud_layout_controller_test.dart`
+were fully rewritten for the int grid fields, per the ticket's Tests section (JSON
+round trip, malformed/old-shaped-JSON fallback, `defaultFor` non-overlap and
+visibility, `clampedToGrid` edge/floor/ceiling/shrink-before-reposition cases,
+`hudRectsOverlap` touching/disjoint/containing/partial cases, `nextFreeSlot` colliding
+and empty/hidden-occupied cases, controller collision-rejection for both
+`updatePosition` and `updateSize`, and `setVisible`'s free-slot fallback). Also updated:
+`test/config_test.dart` (its `HudWidgetLayout` literal and JSON fixtures used the old
+field names — updated to the grid fields, plus one new case for old-shaped JSON) and
+`test/hud_edit_overlay_test.dart` (its `.x`/`.y` assertions became `.col`/`.row`; added
+the two ticket-requested widget tests for a collision-rejected drag and a
+collision-rejected resize, plus two more building `DraggableResizableHudWidget`
+directly at `1x1` and `hudMaxColSpan x hudMaxRowSpan` to assert `tester.takeException()`
+is `null` — the established no-overflow pattern already used in
+`settings_screen_test.dart`).
+
+Final count: **392 tests passing** (up from the 374 baseline), `flutter analyze` clean.