feat(tiles): tile header (status dot, name, menu, remove) and the in-tiles tab marker

Every tile gets a fixed-height header above its body: `● name ......... ⋯ ×`.

- The dot is the six-state classifier the tab rows and both home screens
  share (_sidebarRichRow), with the existing .home-sessions-dot--* classes;
  hovering the header says the state and for how long ("working 3m"). A
  tile whose session waits on a permission prompt or question gets a pulsing
  red border (box-shadow only, never layout; still under reduced motion).
- The name is text with data-i18n-skip; a double-click renames it through
  the tab rename's own write queue (Enter or leaving the field commits,
  Escape cancels, an IME composition owns Enter), and an in-flight name shows
  as already applied, as on the tab.
- ⋯ is the tab rail's session menu (options, new window, close session with
  its confirm); × removes the tile ONLY, the session keeps running. Neither
  button focuses a tile that is not focused.
- The header is fixed at 24px so nothing in it can resize the body, and with
  it the xterm and its PTY (#464).

Every tab render refreshes the headers, so they follow status and name
changes. Tabs of tiled sessions carry .in-tiles (both render paths), and the
tab strip re-renders when tiles come and go.

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

test/mocks/tile-grid-vm.ts

@@ -36,6 +36,24 @@ export class FakeEl {
     this.className = [...set].join(' ');
     return on;
   }
+  append(...children: FakeEl[]) {
+    for (const child of children) this.appendChild(child);
+  }
+  replaceWith(other: FakeEl) {
+    const parent = this.parentElement;
+    if (!parent) return;
+    other.remove();
+    const i = parent.children.indexOf(this);
+    parent.children.splice(i, 1, other);
+    other.parentElement = parent;
+    this.parentElement = null;
+  }
+  title = '';
+  textContent = '';
+  value = '';
+  type = '';
+  focus = vi.fn();
+  select = vi.fn();
   appendChild(child: FakeEl) {
     child.remove();
     child.parentElement = this;