keep bent streets, enclosed landmarks and same-name outlines honest

A street ribbon that holds neither its ring mean nor the anchor is centred
on the street's nearest point when the street runs within 100 m.

Nominatim outline selection ranks an exact name, then one holding every
asked word, then an overlap, and refuses an overlap whose name lacks the
ask's last word unless that word is in the result's address or type, so
"Central Park Zoo" is no longer Central Park. The server caches every
accepted outline and answers each ask with the one holding its resolved
anchor (sent as alat/alon), read across the antimeridian.

A duplicate mark that fails to clean up no longer tears down the new
outline it duplicates.

changelog.d/842-voice-outlines.md

@@ -37,3 +37,8 @@
 - Outline nothing from tiles when the tile under the point failed to load, so a
   neighbouring building or area never stands in for it, and match each of a
   Nominatim name tag's ";"-separated names (manjunath22466, #842).
+- Keep bent streets outlined when the geocoded point sits beside the
+  centreline, never answer a landmark ask with the park or square around it,
+  pick the same-name Nominatim outline that holds the resolved place, and keep
+  a new outline when an identical older mark fails to clean up
+  (samehkhamis, #842).