Replace split lat/lon inputs with single combined coordinate field

[Copilot]

On macOS, pasting coordinates into separate Latitude/Longitude fields drops minus signs, commas, and decimal points, making manual coordinate entry unreliable. Consolidates the two fields into one "lat, lon" string input.

Changes

• OsmLevelLoader — new TryParseCoordinates(string, out double, out double) static helper: splits on first comma, trims whitespace, parses each part with invariant culture
• CoordinateEntryHud (IMGUI in-game dialog) — merged _latStr/_lonStr → single _coordsStr; added hint label e.g. 51.5074, -0.1278
• StartupMenuUi (uGUI startup menu) — merged _latField/_lonField → single _coordsField with ContentType.Standard so all characters (minus, comma, period, space) paste freely; panel height reduced 40px
• OsmLevelLoaderTests — 11 new unit tests for TryParseCoordinates covering valid inputs, whitespace variants, null/empty, missing comma, and non-numeric parts

"51.5074, -0.1278"   → lat=51.5074  lon=-0.1278  ✓
"-33.8688, -70.6693" → lat=-33.8688 lon=-70.6693 ✓
"51.5074 -0.1278"    → false (no comma)           ✗
"abc, def"           → false (non-numeric)         ✗

Original prompt

Rework the coordinates input menu - instead of two separate fields, parse the coordinates from a single input string. On mac, coordinates don't copy paste strings correctly, minus, comma, and decimals don't get pasted.

on the new single input, do validation to make sure there's a comma separating two decimal numbers

---

💡 You can make Copilot smarter by setting up custom instructions, customizing its development environment and configuring Model Context Protocol (MCP) servers. Learn more Copilot coding agent tips in the docs.