fix(ai-chat): style GFM tables in assistant chat markdown

Assistant answers containing GFM tables rendered badly in the narrow AI
side panel: `.markdown` only styled p/pre/code/ul/ol and had no table
rules, so tables used the browser default `table-layout: auto`. Combined
with the inherited `word-break: break-word`, columns collapsed to a
single glyph and headers wrapped mid-word ("Секция" -> "Секци / я").

Add table styling scoped to `.markdown`, in line with the editor's
table.css house style:
- make the table a horizontally scrollable block (display:block +
  overflow-x:auto) so wide tables scroll instead of squishing;
- give cells a 6em min-width and restore word-boundary wrapping
  (word-break:normal + overflow-wrap:break-word);
- add 1px borders, padding and a th background (light-dark for dark
  mode); zero out the default <p> margin inside cells.

CSS-only; no markdown-pipeline change (marked already emits GFM tables,
DOMPurify already allows table tags). Applies to the public share too.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

apps/client/src/features/ai-chat/components/ai-chat.module.css

@@ -55,6 +55,45 @@
     padding-inline-start: 1.4em;
 }
 
+/* GFM tables in assistant markdown. The chat lives in a NARROW side panel, so a
+   wide LLM table must scroll horizontally instead of collapsing its columns:
+   `.markdown` sets `word-break: break-word`, which (with the default table
+   layout) shrinks columns to a single glyph and wraps headers mid-word
+   ("Секция" -> "Секци / я"). Make the table a horizontally scrollable block,
+   give cells a readable minimum width, and restore word-boundary wrapping. */
+.markdown table {
+    display: block;
+    /* lets the table scroll horizontally on its own */
+    max-width: 100%;
+    overflow-x: auto;
+    border-collapse: collapse;
+    margin-block-end: 0.5em;
+}
+
+.markdown th,
+.markdown td {
+    border: 1px solid light-dark(var(--mantine-color-gray-3), var(--mantine-color-dark-4));
+    padding: 3px 8px;
+    /* readable floor; the block scrolls when the row exceeds the panel */
+    min-width: 6em;
+    text-align: left;
+    vertical-align: top;
+    /* cancel the inherited break-word so words don't split mid-glyph */
+    word-break: normal;
+    /* still wrap genuinely long words / URLs at the cell edge */
+    overflow-wrap: break-word;
+}
+
+.markdown th {
+    background: light-dark(var(--mantine-color-gray-1), var(--mantine-color-dark-5));
+    font-weight: 600;
+}
+
+/* GFM wraps cell text in <p>; drop its default block margin inside cells. */
+.markdown table p {
+    margin: 0;
+}
+
 /* Animated three-dot "typing" indicator shown while the agent is thinking but
    has not yet produced any visible text/tool parts. */
 .typingDots {