Nation-op proposals (P4a, #16): protocol types, pendingNationOps state, engine propose/resolve (stage 1)

- shared/protocol.ts: RenameOp/SplitOp/MergeOp + NationOp union; TurnResult.nationOps (required); ConfirmNationOp/RejectNationOp request+response types
- shared/types.ts: GameState.pendingNationOps (type-only import of NationOp — no runtime cycle)
- server/engine.ts: validateNationOps parser wired into validateTurnResult; isMeaningful counts proposals; applyTurnResult appends to the surviving pending list (never applies); runTurn fallback literal; system prompt gains the nationOps JSON field + rename proposal rule (both modes); new resolveNationRef/applyNationOp/confirmNationOp/rejectNationOp (id-first then unique case-insensitive name; rename changes Nation.name only; split/merge no-op until P4b; index validation returns null for 400)
- server/db.ts: legacy rows load with pendingNationOps defaulted to []
- server/index.ts: fresh games start with pendingNationOps: []
- server/stub.ts: deterministicTurn returns nationOps: [] (the stub never proposes — unit-only coverage, matching P3)
- tests: fixture updates (engine/db/map/regions) + new suites for resolveNationRef, validateNationOps, proposal lifecycle, confirm/reject (151 tests total)

server/db.test.ts

@@ -24,6 +24,7 @@ function makeState(id: string): GameState {
     pending: [],
     version: 1,
     unowned: [],
+    pendingNationOps: [],
   };
 }
 
@@ -85,6 +86,17 @@ describe('openDb', () => {
     db.close();
   });
 
+  it('(v0.23 #16 P4a) a legacy row saved before the pendingNationOps field existed loads with it defaulted to []', () => {
+    const db = openDb(':memory:');
+    const legacy = makeState('legacy');
+    delete (legacy as { pendingNationOps?: unknown[] }).pendingNationOps; // a pre-v0.23 save (field absent)
+    db.save(legacy);
+    const loaded = db.load('legacy');
+    expect(loaded).not.toBeNull();
+    expect(loaded!.pendingNationOps).toEqual([]);
+    db.close();
+  });
+
   it('delete removes a game by id and reports absence otherwise', () => {
     const db = openDb(':memory:');
     db.save(makeState('a'));