fix(preview): bound rich-text run walks, fold format notices, match Excel number display

- richTextPrefix visits at most maxCellTextChars + 1 runs. An empty run adds
  no text, so a length check alone walked every run of a shared string for
  every cell referencing it, on every tile.
- Two or more unsupported number format warnings in a tile fold into one
  "N unsupported number formats" entry, and the notice bar has a max-height
  and scrolls.
- General-format and unsupported-format numbers render at 15 significant
  digits, as Excel does (0.1+0.2 shows 0.3).
- TIME_FORMAT accepts a trailing AM/PM, so h:mm AM/PM renders as 2:30 PM
  instead of falling back to a date.
- SPREADSHEET_ASSET_VERSION refreshed.

src/web/public/styles.css

@@ -19318,6 +19318,10 @@ html[data-session-list="sidebar"][data-sidebar="collapsed"] .btn-sidebar-toggle
 
 .spreadsheet-preview-notice {
   flex: 0 0 auto;
+  /* A long warning list scrolls inside the bar instead of pushing the grid out of view. */
+  max-height: 4.5em;
+  overflow-y: auto;
+  overflow-wrap: anywhere;
   padding: 5px 10px;
   color: var(--warning, #f59e0b);
   font-size: 12px;