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)

server/stub.ts

@@ -24,6 +24,13 @@ export interface StubPayload {
    * reads the frontier from the prompt instead.
    */
   frontier?: string[];
+  /**
+   * (v0.22, #16 P3) Region keys currently in no man's land (`state.unowned`),
+   * emitted by the engine's user prompt. The stub ignores this field — it
+   * never releases a region (see deterministicTurn), so no-man's-land behavior
+   * is covered by unit tests against applyTurnResult, not by the stub.
+   */
+  unowned?: string[];
 }
 
 function truncate(s: string, n: number): string {
@@ -45,6 +52,11 @@ function truncate(s: string, n: number): string {
  * content in one round), so the frontier comes from the prompt payload, not
  * from a getNeighbours call. With an empty frontier (no controllable border)
  * no territory change is emitted, keeping every existing assertion stable.
+ *
+ * (v0.22, #16 P3) The stub NEVER releases a region to no man's land (it
+ * always returns `unowned: []`) — e2e assertions rely on its fully-deterministic
+ * one-conquest behavior, so the release/re-claim path is exercised by unit
+ * tests only (see server/engine.test.ts).
  */
 export function deterministicTurn(p: StubPayload): TurnResult {
   const state = p.state;
@@ -108,6 +120,7 @@ export function deterministicTurn(p: StubPayload): TurnResult {
     stateChanges: [{ nation: pid, stat: 'military', op: 'set', value: mil }],
     relations: otherId ? [{ a: pid, b: otherId, set: 'ally' }] : [],
     territoryChanges,
+    unowned: [], // the stub never creates no man's land (see doc comment)
   };
 }