fix(ext): get_totp handles Totp items, not just Login

Critical bug caught in T8 code review: the SW's get_totp handler
gated on core.type === 'login' and referenced core.totp, so the
standalone Totp item type (which lands in T8 with core.type === 'totp'
and core.config) had its detail-view ticker silently rejected with
'no_totp' every second. Ticker swallowed the error; rotating code
display stayed at placeholder forever.

Fix: extend the handler to resolve TotpConfig from either carrier:
- Login items: item.core.totp (optional subfield)
- Totp items:  item.core.config (required)

Also:
- Add 3 router tests covering both paths + the empty case
- Remove stale '……' placeholder check in types/totp.ts's \`t\`
  keyboard shortcut (dead code — the placeholder is '·····' or
  '······', never horizontal ellipses)

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

extension/src/popup/components/types/totp.ts

@@ -125,7 +125,7 @@ export async function renderDetail(app: HTMLElement, item: Item): Promise<void>
         // Copy the currently displayed rotating code.
         const codeEl = document.getElementById('totp-code');
         const code = codeEl?.textContent?.trim();
-        if (code && code !== '……' && code !== '·····' && code !== '······') {
+        if (code && code !== '·····' && code !== '······') {
           try { await navigator.clipboard.writeText(code); } catch { /* swallow */ }
         }
         break;