feat(studio): links to the live site and honest publish feedback - #75

Studio had no visible link to the live site: the only "Visit" was a row menu in Settings › Domains. Publish feedback also didn't link to what went live, and "Page published" was misleading, because marking an item published only flags it until the next site publish.

What people see

1. "View site" in the top bar, left of Publish. Icon-only on phones; the tooltip names the host. It is disabled with a reason when the site has no domain ("Add a domain in Settings") or was never published. Also "Open site" in the site switcher and the ⌘K palette.
2. Publish toasts get "View site" and "Copy link". Rollback and approval toasts get "View site". useToast().success takes up to two actions (DESIGN.md §2n). Without a domain the toast stays plain.
3. An honest item notice: "Marked published · It goes live the next time the site is published", with a "Publish site" action (only with publish rights) that opens the top-bar dialog. It replaces "Page published".
4. The full address in the editors, with copy (ClipboardText):
   • "Live at" when the live snapshot serves that item at that address. This is exact: the editor reads the item from the live snapshot.
   • "Will be at" otherwise.
   • Only the path without a domain; articles in other locales show the path until locale prefixes come.
5. Overview Status card: "Live at" (external link) and "Last published".
6. Pages and Articles rows: "View live" and "Copy link".

Checks

• Studio tests 1168/1168, including the new live-site.test.tsx. Typecheck, design lint and the size ratchet pass (baseline tightened).
• i18n: English plus drafts for 18 languages (not marked reviewed).
• Visual: design:shots at 1440 and 390 px, with a local test account on a local Studio, for the overview, Pages and Articles. No sideways scroll, no console errors; "View site" and the Status card render as intended.
• Bundle budget: 418.8 / 420 kB gzip. The address and row links are split out of the initial load, but only about 1.2 kB of headroom is left.

Follow-ups

• "View live" in the editor header (needs locale prefixes in core-ts).
• An unpublished-changes badge.
• "Last published" uses the live snapshot's createdAt, so a rollback shows when that snapshot was taken.

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