fix(web-ui): display all human-facing timestamps in Asia/Jerusalem (deterministic)

Storage stays UTC (DB TIMESTAMPTZ, API ISO-UTC) — only the display layer is
localized, and now deterministically: every timestamp renders pinned to
Asia/Jerusalem via a single Intl-based formatter, so SSR (UTC container) and
the browser agree on any runtime. No layout/visible-format change — only the tz.

- New single date formatter web-ui/src/lib/format-date.ts (G2): formatDate /
  formatDateShort / formatDateLong / formatDateTime / formatDateTimeFull /
  formatTime / formatIsoDate + Israel helpers getIsraelYear / israelDayKey /
  israelMidnightMs / israelParts + formatRelative (long/short/tight wording).
- Routed all ad-hoc toLocaleDateString/toLocaleTimeString/toLocaleString +
  hand-rolled new Date(...).get*() / toISOString().slice(0,10) timestamp call
  sites (30 files) through it. Number toLocaleString left untouched.
- Spec: added INV-UI9 to docs/spec/X6 (UTC storage, Asia/Jerusalem display).

Display-only; no layout/design/IA change → Claude Design gate N/A.
Invariants: G2 (single date formatter, no parallel ad-hoc formatting), INV-UI9.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

web-ui/src/app/settings/_components/agents-tab.tsx

@@ -19,6 +19,7 @@ import {
   type DriftEntry,
   type PaperclipAgent,
 } from "@/lib/api/paperclip-agents";
+import { formatDateShort } from "@/lib/format-date";
 
 const ROLE_LABEL: Record<string, string> = {
   ceo: "CEO",
@@ -211,7 +212,7 @@ function PairCard({ pair }: { pair: AgentPair }) {
           </Button>
           {pair.master?.updated_at && (
             <span className="text-[0.7rem] text-ink-light">
-              עודכן: {new Date(pair.master.updated_at).toLocaleDateString("he-IL")}
+              עודכן: {formatDateShort(pair.master.updated_at)}
             </span>
           )}
         </div>