fix(maps): preserve configured legacy light tile URL overrides #364

Confirmed problem

After PR #344, the shared getTileUrl() consults the tile registry before the existing light URL override. The registry always supplies a default provider, so an operator's tiles.light or map.tiles.lightUrl is ignored when no provider was explicitly selected.

This remains on master ff9a501c17396aada504e87d44c0f503e2740b8e. Parent-versus-merge checks reproduced both configuration shapes in production JavaScript and Chromium: the parent returned the configured URL; the merged code returned the default provider URL.

Required correction

• Preserve both existing configuration formats for the affected shared inset-map callers.
• Keep explicit provider selection functional, with a documented and tested precedence rule.
• Preserve dark/inverted tiles, attribution and tile-error recovery behavior.
• Do not add a new setting or hard-code another provider URL.

Acceptance checks

Cover each configuration shape with and without an explicit provider choice, and test actual browser tile requests using intercepted synthetic URLs. Include the registry's normal fallback cases.

This is a compatibility follow-up to the closed tile-fallback issue #332. The separate provider zoom-limit gap is outside this issue's scope.