swarm-ui: don't break at a narrow viewport

Closes #3447.

- Shell.css: .shell-header and .shell-nav wrap onto a second line
  below a breakpoint instead of forcing horizontal overflow — no
  hamburger/collapse menu, per mara's own 'don't break, don't
  over-invest' scoping.
- LinksMenu.css: bumped .links-menu-button and .links-menu-item to the
  same 2.75em (~44px, WCAG 2.5.5) touch-target floor the shared ui/
  kit's form controls and buttons already carry — this trigger is
  bespoke, not built from that kit, but the floor applies regardless.
- Table.tsx/.css: wrapped the table in a .ui-table-scroll container
  (overflow-x: auto) so a wide table scrolls within its own box on a
  narrow viewport instead of forcing the whole page to overflow
  horizontally — not named in the issue's two concrete spots, but the
  same 'should not break' failure mode, and fixing it at the shared
  Table primitive covers every future caller.

.create-agent-input's fixed width -> max-width was already fixed as
part of #3448's form kit.

Verified: tsc clean, build succeeds, screenshotted at 320px (hives
nav wraps, table scrolls internally, page itself doesn't overflow)
and 480px (create-agent form fields fit).

frontend/packages/swarm-ui/src/shell/Shell.css

@@ -2,10 +2,17 @@
    renders into. Colour vars come from ../theme.css (same base16 slots
    the per-hive dashboard uses, so this reads as recognizably
    hyperhive) — the layout itself is this package's own, not
-   @hive/shared's chrome.css. */
+   @hive/shared's chrome.css.
+
+   `flex-wrap` on the header and nav rather than a hamburger/collapse
+   menu: a narrow viewport (phone or a tiled desktop window) wraps onto
+   a second line instead of overflowing — "don't break, don't
+   over-invest" is the explicit scope here, not full mobile navigation
+   redesign. */
 .shell-header {
   display: flex;
   align-items: center;
+  flex-wrap: wrap;
   gap: 1.5em;
   padding: 0.75em 1.25em;
   border-bottom: 1px solid var(--border);
@@ -18,6 +25,7 @@
 }
 .shell-nav {
   display: flex;
+  flex-wrap: wrap;
   gap: 1em;
 }
 .shell-nav-link {