v0.27.0 (#44): LLM-placed named map point markers

- shared: 8 MarkerTypes + MARKER_TYPE_INFO (label/color/glyph); MapMarker;
  GameState.markers (required, [] at init); TurnResult.markers {add,remove};
  MarkerSpec/MarkerInfo; FNV-1a 4-char markerId; MAX_MARKERS=400.
- data: new public/region-centroids.json (1,800 anchors = largest-part centroid
  + spread ~0.1x min-bbox) built by new idempotent scripts/build-region-centroids.mjs.
- server: regions.ts centroid loader (public/ then dist/); engine applyTurnResult
  marker ops (remove -> owner-recompute -> add, jitter, cap, never throws);
  prompt documents the contract; buildUserPrompt carries markers; stub marker-free.
- client: WorldMap symbol layer rendered as canvas per-type icons (glyph CDN dead);
  hover tooltip shows name; click focuses owning nation.
- tests: 168 -> 189 (centroids script, regions centroids, db legacy, engine markers).

server/stub.ts

@@ -31,6 +31,13 @@ export interface StubPayload {
    * is covered by unit tests against applyTurnResult, not by the stub.
    */
   unowned?: string[];
+  /**
+   * (v0.27, #44) Current map markers (`{ id, type, name, regionKey, owner }`),
+   * emitted by the engine's user prompt. The stub ignores this field — it
+   * never places or removes a marker (see deterministicTurn), so the marker
+   * path is covered by unit tests against applyTurnResult, not by the stub.
+   */
+  markers?: Array<{ id: string; type: string; name: string; regionKey: string; owner: string | null }>;
 }
 
 function truncate(s: string, n: number): string {
@@ -61,6 +68,10 @@ function truncate(s: string, n: number): string {
  * (v0.23, #16 P4a) The stub likewise NEVER proposes nation-management ops (it
  * always returns `nationOps: []`) — the propose→confirm/reject flow is
  * covered by unit tests only, keeping the e2e assertions untouched.
+ *
+ * (v0.27, #44) The stub likewise NEVER places or removes a map marker (it
+ * always returns `markers: { add: [], remove: [] }`) — the marker path is
+ * covered by unit tests only, keeping the e2e assertions untouched.
  */
 export function deterministicTurn(p: StubPayload): TurnResult {
   const state = p.state;
@@ -126,6 +137,7 @@ export function deterministicTurn(p: StubPayload): TurnResult {
     territoryChanges,
     unowned: [], // the stub never creates no man's land (see doc comment)
     nationOps: [], // the stub never proposes nation ops (see doc comment)
+    markers: { add: [], remove: [] }, // the stub never touches markers (see doc comment)
   };
 }