Show session status as a badge on the detail page

Reuses SessionsTable's STATUS_VARIANT mapping (now exported) so the
detail page's status matches the table's badge instead of plain text.
Also drops the now-stale px-1.5 alignment padding on the meta lines
now that the title input carries no horizontal padding of its own.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01WzyfRyA7h5rs5SCAahLAWd

components/sessions/SessionsTable.tsx

@@ -25,7 +25,7 @@ export interface SessionRow {
   durationMs: number | null;
 }
 
-const STATUS_VARIANT = {
+export const STATUS_VARIANT = {
   active: "default",
   completed: "secondary",
   aborted: "destructive",