feat(tabs,app): tab id handles, fixed-width tabs-lift, slim shell + full-height sidebar

Tabs:
- short-handle ID badge per tab (shortest unique conversationId prefix, min 4)
- fixed-width (w-48) tabs with tabs-lift folder borders

Shell (composition root):
- drop the Dispatch title bar; tabs sit at the very top with a 5px gap
- big faded "Dispatch" watermark centered on an empty chat
- collapsible right sidebar (empty shell) spanning full window height: a
  permanently right-pinned hamburger in the tab row toggles it; in-flow push
  that shrinks the whole left column (tabs included) at >=lg, overlay + backdrop
  below lg; open-by-default on wide / closed on narrow
- main is overflow-hidden with a min-w-0 shrink chain; app.css pins
  html/body/#app height + body overflow hidden so the page never overflows

1 files changed, 12 insertions, 0 deletions

diff --git a/src/app.css b/src/app.css
index 37131d3..5db1f25 100644
--- a/src/app.css
+++ b/src/app.css
@@ -6,3 +6,15 @@
 @plugin "daisyui" {
 	themes: dracula --default;
 }
+
+/* App shell fills the viewport and never scrolls/overflows at the page level —
+   the inner regions (tab strip, chat transcript) own their own scrolling. */
+html,
+body,
+#app {
+	height: 100%;
+}
+
+body {
+	overflow: hidden;
+}