sanWriter.sanOf doesn't return a SAN

But something that looks like a SAN, yet misses check flag and proper
disambiguation. I'm calling it an `AlmostSan`.

`speakable(san: San)` won't work properly if passed an `AlmostSan`.

I wish types could help us differentiate the two.

ui/@types/lichess/index.d.ts

@@ -249,6 +249,7 @@ type Perf = Exclude<VariantKey, 'standard'> | Speed;
 
 type Uci = string;
 type San = string;
+type AlmostSan = string;
 type Ply = number;
 type Seconds = number;
 type Centis = number;

ui/chess/src/sanWriter.ts

@@ -84,7 +84,11 @@ function slidingMovesTo(s: number, deltas: number[], board: Board): number[] {
   return result;
 }
 
-export function sanOf(board: Board, uci: string): San {
+/* Produces a string that resembles a SAN,
+ * but lacks the check/checkmate flag,
+ * and probably has incomplete disambiguation.
+ * But it's quick. */
+export function almostSanOf(board: Board, uci: string): AlmostSan {
   if (uci.includes('@')) return fixCrazySan(uci);
 
   const move = decomposeUci(uci);
@@ -96,7 +100,7 @@ export function sanOf(board: Board, uci: string): San {
 
   // pawn moves
   if (pt === 'p') {
-    let san: string;
+    let san: AlmostSan;
     if (uci[0] === uci[2]) san = move[1];
     else san = uci[0] + 'x' + move[1];
     if (move[2]) san += '=' + move[2].toUpperCase();
@@ -140,7 +144,7 @@ export function sanWriter(fen: string, ucis: string[]): SanToUci {
   const board = readFen(fen);
   const sans: SanToUci = {};
   ucis.forEach(function (uci) {
-    const san = sanOf(board, uci);
+    const san = almostSanOf(board, uci);
     sans[san] = uci;
     if (san.includes('x')) sans[san.replace('x', '')] = uci;
   });

ui/round/src/ctrl.ts

@@ -48,7 +48,7 @@ import type {
 import { defined, type Toggle, toggle, requestIdleCallback } from 'common';
 import { storage, once, type LichessBooleanStorage } from 'common/storage';
 import { pubsub } from 'common/pubsub';
-import { readFen, sanOf, speakable } from 'chess/sanWriter';
+import { readFen, almostSanOf, speakable } from 'chess/sanWriter';
 
 interface GoneBerserk {
   white?: boolean;
@@ -342,7 +342,7 @@ export default class RoundController implements MoveRootCtrl {
 
     if (!meta.preConfirmed && this.confirmMoveToggle() && !meta.premove) {
       if (site.sound.speech()) {
-        const spoken = `${speakable(sanOf(readFen(this.stepAt(this.ply).fen), move.u))}. confirm?`;
+        const spoken = `${speakable(almostSanOf(readFen(this.stepAt(this.ply).fen), move.u))}. confirm?`;
         site.sound.say(spoken, false, true);
       }
       this.toSubmit = move;