Make every settings row reachable, and every accessibility switch honest

Claude-Session: https://claude.ai/code/session_01Ms2FbjQy31TVf3CEvQhGM8

config/dot/quickshell/modules/settings/README.md

@@ -335,6 +335,30 @@ erase a user-selected accent or a theme switch to leave the border behind.
 | `ChoiceRow { setting }` | An enum, as a segmented control |
 | `ActionRow` | A button: opens a GNOME panel, runs a one-shot |
 | `TextRow` | A genuinely read-only fact |
+| `SettingsNote` | An inset paragraph: the explanation too long to be a `detail` |
+
+`SettingsNote` is deliberately quiet and must stay that way. It explains
+absences and boundaries — what this session cannot do, and why — and a
+warning-coloured box would turn "not offered yet, here is the reason" into
+"something is wrong here".
+
+### The rows are keyboard-reachable
+
+Every row primitive carries `Accessible.role`, an `Accessible.name` taken from
+its label, and an `Accessible.description` taken from its detail; the
+interactive element sets `activeFocusOnTab` and draws a two-pixel
+`Theme.accentSecondary` ring **only** while it holds focus. Tab walks the page,
+Space and Enter flip a switch or press a button, and Left/Right (and Up/Down)
+step a slider by one schema step or move a segmented choice by one option,
+never wrapping.
+
+Two rules hold this together. An inert row is not a Tab stop: `SettingRow`
+becomes focusable only when `activatable` is true, because Tab landing on
+static text is how keyboard navigation stops being usable. And a keyboard
+change commits through exactly the same path a pointer change does —
+`SliderRow`'s arrows go through the same 140 ms debounce as a drag, so a held
+arrow behaves like a drag rather than a burst of writes the compositor spends
+the whole time rejecting.
 
 `TextRow` is for facts, not for settings that were merely expensive to wire.
 Before Stage 3 more than half of all rows were static text standing in for