fix(i18n): zh-CN for the case picker rows, Bottom bar settings, new toasts, tile and spreadsheet text

- Case picker: the "New or link a case…" and "Case settings…" rows that
  replaced the translated + and gear buttons get zh-CN entries reusing the
  buttons' wording, plus the list's "No cases match".
- App Settings, Bottom bar: the whole group translates as one (heading, the
  four Git status rows with #543's max repositories and git timeout, and
  their descriptions), so it never reads half English. The Git panel's two
  button names, which the new "Git status" key reaches, read naturally too.
- Toasts: the three "Could not open a new window for this ..." errors and
  the dictation-closed warning.
- Spreadsheet preview: "Spreadsheet preview failed (<status>)" gets a
  pattern. Worker refusals map their error code to one user sentence each in
  the renderer (the raw message goes to the console), feature ids read as
  words (pivot tables, external links), and the notice bar translates each
  item before the join; a number format's code passes through untouched.
  The worker and core are unchanged, so their pinned strings and the
  asset version hash stay as they were.
- Header Stats Style Tiles: the connection tile's value word reads in
  Chinese through scoped "Connection tile: <word>" keys, never bare-word
  keys ("retry" is also the orchestrator's Retry button, "LIVE" a resume
  list badge). The indicator cache now includes the UI language, so a
  language switch repaints it on the next update.
- Tile grid: the "Loading…" label was CSS content text the translator
  cannot reach; it is now content: attr(data-loading-label), written through
  the translator when the tile is built and each time it starts loading.

Tests pin every new string (zh differs, no English left, English unchanged)
and fail without these changes: the tile harvest sees the loading label and
the rename field, a CSS guard keeps words out of tile generated content, the
Bottom bar group, the case picker rows and toasts read from their source,
the connection tile across a language switch, and the spreadsheet error
codes, notice bar and status line.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

src/web/public/styles.css

@@ -19843,9 +19843,11 @@ body.tile-grid-resizing--row * {
 }
 
 /* Quiet "loading" state while the tile's capture waits in the grid's one load
-   queue (or runs). */
+   queue (or runs). The text is the body's data-loading-label, which tile-grid.js
+   writes in the UI language (_setTileLoadingLabel): generated content is out of
+   the i18n layer's reach, so no literal words here. */
 .tile.tile--loading .tile-body::after {
-  content: 'Loading\2026';
+  content: attr(data-loading-label);
   position: absolute;
   top: 6px;
   right: 10px;