Document the "Public" naming trap: read-only viewer, not a visibility property

Caught live while explaining PublicDistrictLayers/PUBLIC_SOURCE_ID during
unrelated work on feat/ftv-proportionality-test: "Public" reads as an
access-control term (implying a "private district" counterpart that
doesn't exist) when it actually means "the read-only share-link/Evaluate
viewer," as opposed to MainMap/CoiMap's interactive editor. Added to
map-rendering/SKILL.md's Vocabulary section (the terminology-seam trigger)
and docs/overview.md's page-composition paragraph, which was also missing
PublicMap from the MapPage.tsx composition entirely.

Author: fangge518

agent-skills/map-rendering/SKILL.md

@@ -27,6 +27,12 @@ user-invocable: false
   (`ACTIVE_TOOLS.SHATTER`, ~45 files); the toolbar label is "Break"; user copy says
   "break down into blocks"; the pill component is `BlockModePill`; the tool is gated
   behind "Super Draw" mode. Grepping the UI word "break" misses the implementation.
+- **"Public" means "read-only viewer," not a permissions/visibility property**:
+  `PublicMap`/`PublicDistrictLayers`/`PUBLIC_SOURCE_ID` render a plan's already-computed
+  district geometry (`GET /document/{id}/stats`) for the share-link/Evaluate view;
+  `MainMap` is the interactive block-level editor, picked instead via `isPublicPage` in
+  `MapPage.tsx`. There is no "private district" — reading "Public" as an access-control
+  term is the trap.
 
 ## Where the rest lives
 

docs/overview.md

@@ -102,11 +102,16 @@ keys. Cross-store reactions are mostly wired in one place (`store/subscriptions.
 Assignments buffer during a gesture (`accumulatedAssignments`) and ingest once at
 gesture end — one coalesced write, one undo entry.
 
-Page composition: `components/MapPage/MapPage.tsx` → `MainMap.tsx` (district mode) /
-`CoiMap.tsx` (community mode) over a shared `MapContainer.tsx` shell. Layer components
-live under `components/Map/PolygonLayers/`; layer/style constants under
-`constants/map/`; the render subscriber is `utils/map/mapRenderSubs.ts`; MapLibre event
-wiring is `utils/events/mapEvents.ts`.
+Page composition: `components/MapPage/MapPage.tsx` picks, via `isPublicPage`, between the
+interactive editor — `MainMap.tsx` (district mode) / `CoiMap.tsx` (community mode) — and
+`PublicMap.tsx`, the read-only map shown on a plan's share-link/Evaluate page. "Public"
+here means "read-only viewer," not a visibility/permissions property, and has no
+"private" counterpart; `PublicMap` renders pre-aggregated district geometry fetched from
+`/document/{id}/stats`, not the live block-level assignment state the editor works from.
+All three sit over a shared `MapContainer.tsx` shell. Layer components live under
+`components/Map/PolygonLayers/`; layer/style constants under `constants/map/`; the render
+subscriber is `utils/map/mapRenderSubs.ts`; MapLibre event wiring is
+`utils/events/mapEvents.ts`.
 
 ## Saving and syncing