attribution: in-game ODbL credit via AGigLineHUD

The demo is built from OpenStreetMap data (ODbL 1.0) and needs attribution
wherever the derived work is shown. Add it to the running game, not just the
documents.

- AGigLineHUD (C++): plain AHUD::DrawText in the bottom-left draws
  '(c) OpenStreetMap contributors' and 'Data (c) OpenStreetMap contributors,
  ODbL 1.0 - openstreetmap.org/copyright', with a shadow pass for legibility
  over bright pavement and sky. No UMG widget asset, so a cook cannot drop it
  through a missing widget reference.
- AGigLineGameModeBase: HUDClass = AGigLineHUD, so the credit is on by default.
- AGigLineShotActor: screenshots are now requested with the UI shown, so the
  attribution appears in every capture under Screenshots/ and the obligation
  is provable in review rather than only described.

Docs: THIRD_PARTY_NOTICES records that the string is displayed in-game;
Screenshots/README documents the overlay; TODO marks the item done and
narrows the remaining ODbL question to the shipped-derivative-database
posture.

THIRD_PARTY_NOTICES.md

@@ -25,6 +25,8 @@ Status values: **verified** (licence confirmed and permits our use), **pending**
 
 Attribution string for any OSM-derived output: "© OpenStreetMap contributors", <https://www.openstreetmap.org/copyright>. The data is available under the [Open Database License 1.0](https://opendatacommons.org/licenses/odbl/1-0/).
 
+This attribution is **displayed in the running game**, not only in this document: `AGigLineHUD` (`Game/GigLine/Source/GigLine/GigLineHUD.cpp`) draws the credit and the licence URL in the bottom-left of every frame, so the obligation is met by the shipped build. It is visible in every capture under `Screenshots/` because the screenshot actor requests screenshots with the UI shown.
+
 ## Reference photography (local only, not committed, not shipped)
 
 Reference photographs are **not** part of this repository. They live in the gitignored `Art/reference/` tree on the development machine, are used only for internal, private development, and are never built into a build or shipped. `.gitignore` enforces this; nothing under `Art/reference/` may be added, staged, or committed.