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/index.ts

@@ -22,7 +22,7 @@ import { createLlmClient } from './llm';
 import { makeStubLlmClient } from './stub';
 import { askAdvisor, confirmNationOp, queueRoundItem, rejectNationOp, removeRoundItem, runTurn } from './engine';
 import { buildRegionMap } from './map';
-import { allTerritoryKeys, expandCountriesToKeys, hasAdjacency, loadRegions, neighboursOf, referenceForKeys, validKeys } from './regions';
+import { allTerritoryKeys, centroidOf, expandCountriesToKeys, hasAdjacency, hasCentroids, loadRegions, neighboursOf, referenceForKeys, validKeys } from './regions';
 import { createPresetStore } from './presets';
 import { openDb, type Db } from './db';
 
@@ -134,6 +134,8 @@ app.post('/api/games', (req: Request, res) => {
     // list grows as the LLM proposes renames (and, later, splits/merges) and
     // shrinks as the player confirms or rejects them.
     pendingNationOps: [],
+    // (v0.27, #44) No markers on a fresh game; the LLM places them over time.
+    markers: [],
   };
   // v0.19 (#16 P1): expand each nation's ISO_A3 country list to the region keys
   // of all its sub-regions, so ownership (and the choropleth) is at region
@@ -288,6 +290,11 @@ app.post('/api/games/:id/jump', async (req, res) => {
       // engine the resolver — the turn then runs with the LLM's getNeighbours
       // tool and the player-frontier prompt field (both switch off without it).
       getNeighbours: hasAdjacency() ? (keys) => neighboursOf(keys) : undefined,
+      // (v0.27, #44) when the centroid manifest loaded, hand the engine the
+      // resolver so a turn can place new map markers at their region's
+      // centroid (without it, marker adds are dropped; existing markers are
+      // still maintained).
+      centroidOf: hasCentroids() ? (key) => centroidOf(key) : undefined,
     });
     db.save(state);
     broadcast(id, 'turn', { state, result });