[Bug]: Non-finite distances, areas and coordinates display as "NaN km", "inf km", "-inf m", "NaN° E NaN° N" #938

What happened?

The measurement formatters in crates/geom/src/lib.rs print non-finite values as if they were numbers, and these strings reach the UI:

format_distance(NaN) prints "NaN km" because both m.round() < 1000.0 and (m / 100.0).round() < 1000.0 are false for NaN, falling into the "km branch" with {:.0}.

Callers that pass results through these formatters:

• the measure tool's metric panel (ui-egui/src/measure_units.rs::distance calls geom::format_distance directly) — so any non-finite segment length (for example from a geometry with a NaN vertex, see the companion issue about haversine_m) shows as "NaN km" or "20,015,114 m";
• the scale bar's label (render/src/text.rs);
• route/match error strings built in analysis/src/network.rs.

The tiles router already handles this correctly and shows what I would expect here: tiles/src/routing.rs::format_distance returns "0 m" for non-finite input (its asserts at line 543 cover it).

Steps to reproduce

rustgis_geom::format_distance(f64::NAN) → "NaN km", as in the table above.

Expected behavior

Non-finite distances, areas and coordinates display as an em dash, blank, or are refused upstream so the value never reaches a formatter — consistently with routing::format_distance's existing non-finite handling. Whatever is chosen, the same behaviour should hold for format_distance, format_area, format_lonlat and format_dms, since they are shown side by side in the measure panel and status bar.

Where it may come from

The formatters assume finite input. Adding a non-finite guard at the top of each (mirroring routing::format_distance) is a small, self-contained change; the sooner fix is at the measurement level (companion issue), which stops non-finite values from being produced at all.

How are you running RustGIS?

Desktop app built from source, on Linux (WSL); verified as a library test against rustgis-geom.

Version

main at 342b2b2 (after #928).