P1 exit: chat UI, sessions column, agent create — 11 E2E journeys green

- Stream layer: incremental SSE parser tested against bytes captured from
  the REAL gateway (chunking-independent, UTF-8-safe, heartbeat-tolerant);
  Zod gateway event schemas; pure transcript reducer (optimistic send,
  delta streaming, step traces, resume dedupe, error states)
- Same-origin /api proxy route: httpOnly cookie -> bearer, unbuffered SSE
  passthrough; NuqsAdapter in root layout
- Chat workspace: route /claws/{id}/chat/{key} (RSC history + settings),
  WelcomeState with suggested prompts, MessageList (right user bubbles,
  left agent messages, blink caret), collapsible StepTrace, Composer
  (Enter sends, Shift+Enter newline)
- SessionsColumn in 208px SlidePanel (?sessions=1): search, relative
  times, active coral border, new session; /claws/{id} resumes latest or
  opens fresh; minimal create-claw form; rail + button and roster links
- P1 exit E2E: scripted reply streams, tool step trace survives reload,
  separate transcripts across sessions with column switching, create claw
  and chat immediately

83 Rust + 56 frontend unit/component tests + 11 Playwright journeys.

Co-Authored-By: Claude Fable 5 <[email protected]>

frontend/src/lib/format/relative-time.ts

@@ -0,0 +1,18 @@
+/** Compact relative timestamps for session rows (§6): "4h ago". */
+export function relativeTime(iso: string, now: Date = new Date()): string {
+  const then = new Date(iso).getTime();
+  const seconds = Math.max(0, Math.floor((now.getTime() - then) / 1000));
+  if (seconds < 60) {
+    return "just now";
+  }
+  const minutes = Math.floor(seconds / 60);
+  if (minutes < 60) {
+    return `${minutes}m ago`;
+  }
+  const hours = Math.floor(minutes / 60);
+  if (hours < 24) {
+    return `${hours}h ago`;
+  }
+  const days = Math.floor(hours / 24);
+  return `${days}d ago`;
+}