No man's land: TurnResult.unowned + release/re-claim in applyTurnResult + distinct grey map rendering (#16 P3)

- shared/protocol.ts: TurnResult.unowned (keys released this turn) + the map
  presentation contract (regionFillStyle / unownedTooltipLabel, hue-less grey)
- shared/types.ts: required GameState.unowned (cumulative mid-game releases;
  [] at init, distinct from preset-unassigned regions)
- server/engine.ts: applyTurnResult applies releases first (sole-owner only,
  never fabricating no man's land from unassigned keys), then claims against
  the post-release snapshot (gain on an ownerless key = re-claim); lone
  release is isMeaningful; prompts + user payload carry the unowned field
- server/stub.ts: unchanged behavior (never releases; e2e stays stable)
- server/db.ts: legacy rows load with unowned defaulted to []
- server/index.ts: create-game sets []; jump reference table includes
  released keys so the model can name them for re-claim
- WorldMap/App: unowned prop -> visible grey + 'No man's land' tooltip
- unit tests: 105 -> 127 (release/re-claim suites, presentation contract,
  legacy-row normalization)

shared/protocol.ts

@@ -46,6 +46,16 @@ export interface TurnResult {
   stateChanges: StateChange[];
   relations: RelationChange[];
   territoryChanges: TerritoryChange[];
+  /**
+   * (v0.22, #16 P3) Region keys that become **unowned** — "no man's land" —
+   * this turn. The engine removes each key from its current (sole) owner so it
+   * ends the turn ownerless and marks it in `GameState.unowned`; the LLM
+   * narrates the cause (war, cataclysm, collapse) in `events`. Re-claiming is
+   * NOT expressed here: a nation re-claims an unowned region with an ordinary
+   * `gain` on that key. Only keys a nation currently owns can be released;
+   * empty on normal turns.
+   */
+  unowned: string[];
 }
 
 /** Per-region map payload: region key -> owning nation + its stable color. */
@@ -188,6 +198,47 @@ export function nationColor(id: string): string {
   return `hsl(${hue} 58% 46%)`;
 }
 
+// --- No man's land (v0.22, #16 P3) — the map presentation contract ---
+//
+// An unowned region has two distinct looks, and the difference is NOT in the
+// RegionMap (a key absent there is simply unowned): it is decided by the
+// client from `GameState.unowned` (the keys released mid-game). The constants
+// and the one decision function live here — shared and pure — so the
+// client's choropleth is the only consumer and the color contract is testable
+// from the server-side tests (shared/*.test.ts is not in the vitest glob).
+
+/** The distinct, visible neutral grey for a **no man's land** region (released mid-game). Hue-less by construction, so it can never collide with a nation's `nationColor` (`hsl(h 58% 46%)`, always chromatic). */
+export const NO_MANS_LAND_FILL = '#3f3f46';
+/** The border of a no-man's-land region (brighter than a plain unowned one). */
+export const NO_MANS_LAND_STROKE = 'rgba(255,255,255,0.25)';
+/** The faint neutral fill for a region no nation owns that was never released mid-game (a preset never assigned it). */
+export const UNOWNED_FILL = 'rgba(148,163,184,0.05)';
+/** The border of a plain unowned region. */
+export const UNOWNED_STROKE = 'rgba(255,255,255,0.14)';
+/** The border of an owned region (brighter than unowned). */
+export const OWNED_STROKE = 'rgba(255,255,255,0.30)';
+
+/** The hover-tooltip sub-line for a region with no owning nation. */
+export function unownedTooltipLabel(isNoMansLand: boolean): string {
+  return isNoMansLand ? "No man's land" : 'No owner';
+}
+
+/**
+ * The fill + border for one sub-region, given its RegionMap entry
+ * (`undefined` = unowned) and whether its key is no man's land (released
+ * mid-game, i.e. in `GameState.unowned`). Pure + shared; see the section
+ * comment above for why the distinction is not encoded in the RegionMap.
+ */
+export function regionFillStyle(
+  owner: RegionOwner | undefined,
+  isNoMansLand: boolean,
+): { fill: string; stroke: string } {
+  if (owner) return { fill: owner.color, stroke: OWNED_STROKE };
+  return isNoMansLand
+    ? { fill: NO_MANS_LAND_FILL, stroke: NO_MANS_LAND_STROKE }
+    : { fill: UNOWNED_FILL, stroke: UNOWNED_STROKE };
+}
+
 /** Rebuild the full event list entry shape from a TurnEventSpec + turn/date. */
 export function makeEvent(
   spec: TurnEventSpec,