fix(draw): show a 9,999.6 m² area as 1.0 ha, not 10000 m²

The draw hint picked m², ha or km² from the raw area and then rounded,
so 9,999.5 m² up to a hectare read "10000 m²" and about 999,500 m² up
to a square kilometre read "100.0 ha". It now rounds first, as the line
measure already does.

docs/CURRENT-STATE.md

@@ -5350,6 +5350,7 @@ request viewbox and continues searching without that geographic preference.
 - Drawn-line distance labels select metres or kilometres after rounding to the nearest metre, so a 999.5-metre line displays as `1.0 km` rather than `1000 m`.
 - **Measurements and centres are computed on unwrapped longitudes** (`unwrapLongitudes` / `wrapLongitude` in `drawMode.js`, used by `ringAreaM2`, `ringCentroid` and the engine's manual-area anchor). A ~50,000 m² rectangle straddling the antimeridian reads its 0.002° width as 359.998° under raw arithmetic: it measured thousands of square kilometres and anchored on the Greenwich meridian, half a world from the shape. Path length was already safe — haversine is periodic in the longitude delta — and a test pins that so a "fix" cannot break it.
 - **Bounds.** One shape holds at most `MAX_VERTICES` = 512 points; two clicks within 0.5 m are one vertex (that is what makes a double-click finish without leaving a stray point); a vertex that is not a finite on-globe coordinate is refused. A shape that encloses nothing is refused rather than placed: three collinear points are not an area and a line under a metre long is not a line, and the hint says which.
+- Drawn-area measures round before choosing m², ha or km², so 9,999.6 m² displays as `1.0 ha`, not `10000 m²`, and 999,960 m² as `1.00 km²`, not `100.0 ha`.
 - Pointer ownership: while a session is open the tool holds the single pointer claim (`claimPointer('draw')`, `src/data/inputOwnership.js`) and **every** ambient scene selection handler — the shared tracking click gesture behind flights, military and CCTV, plus vessels, satellites, launches, fires, installations, bikeshare, radio, submarine cables, the bundled GeoJSON layers and the CCTV calibration gizmo — returns before picking. A vertex over an aircraft is a vertex, not a selection.
 - **The claim is a LEASE.** `claimPointer(owner)` returns an opaque token or `null`; `releasePointer(lease)` takes that token. A second claim fails even under the same owner name, because two live instances of one tool — an old one mid-teardown and its replacement — are two owners; releasing by name let the old instance free the claim its successor was holding, and every layer started selecting through the live session's vertices. A superseded lease now releases nothing.
 - **Cesium's own click actions are borrowed too.** The Viewer binds a selecting LEFT_CLICK and a tracking LEFT_DOUBLE_CLICK on its own handler, outside every layer and therefore outside the shared claim — guarding the layers alone still left a drawn vertex selecting the entity under it. Both are removed for the session and restored, as the same function objects, when it ends or the tool is destroyed.