docs(agents): record the floating map toolbar layout

AGENTS.md

@@ -627,6 +627,17 @@ session with **no other memory of this project**. So:
   say this honestly (2026-09-29). **Still future:** real MLS
   (`ts-mls`) instead of group-key crypto, plus Cordn RPC interop. **Lesson: grep
   `src` for the feature before building it — this was nearly duplicated.**
+- **Map layout — controls float (2026-09-29):** on mobile the `MapPage` toolbar
+  is **`absolute` over the map** (`pointer-events-none` wrapper + gradient +
+  `pointer-events-auto` inner) so the map fills the whole container; `md:static`
+  restores the in-flow bar on desktop. The container height subtracts
+  **header + bottom nav only** (the old desktop `--footer-desktop` subtraction is
+  gone) and the **desktop footer is hidden on full-bleed routes** (`Layout`
+  footer: `isFullBleed ? 'hidden' : 'hidden md:block'`). Result at 390×844:
+  map starts under the header and is **~86% of the viewport** (was ~78%). Don't
+  re-add a stacked toolbar or the footer subtraction. The "New here?" welcome
+  banner (logged-out only) still occupies ~69px *in flow* on first visit — it's
+  dismissible and the dismissal is persisted (`skatespots_welcome_dismissed`).
 - **Empty-map nudge (2026-09-28):** `MapPage` distinguishes the two empties — the
   existing "No spots match" card is for *filters* (`filteredSpots.length === 0 &&
   allLocations.length > 0`) and a new "No spots mapped yet — be the first" card