bug: browser tab uses default Vite favicon + stale 'Claude Agent Manager' title instead of Trinity branding

[vybe]

Summary

The Trinity web app's browser tab shows the wrong favicon and a stale page title. In src/frontend/index.html the favicon still points at the default Vite logo (<link rel="icon" href="/vite.svg">) — and vite.svg isn't even present in src/frontend/public/, so browsers fall back to a generic globe icon — while the <title> reads Claude Agent Manager instead of Trinity's product name. Every open tab therefore misrepresents the product's branding.

Context

Trinity logo/icon assets already exist in the repo, so this is a small wiring fix rather than a design task:

• src/frontend/public/icons/trinity-mobile.svg
• src/frontend/public/icons/trinity-mobile-192.png, trinity-mobile-512.png
• src/frontend/public/icons/apple-touch-icon-mobile.png
• src/frontend/src/assets/trinity-logo.svg, trinity-logo-white.svg, trinity-logo.png

src/frontend/public/mobile-manifest.json already uses the "Trinity" name and these icons — only the desktop index.html was left on the Vite scaffold defaults.

Acceptance Criteria

• src/frontend/index.html favicon points at a Trinity logo asset that actually exists under src/frontend/public/ (no /vite.svg 404).
• Provide an apple-touch-icon link (reuse public/icons/apple-touch-icon-mobile.png) so the icon is correct when saved to a home screen / bookmarked.
• <title> reflects Trinity branding (e.g. Trinity or Trinity — Agent Orchestration), not Claude Agent Manager.
• The browser tab shows the Trinity logo + a sensible title on the local dev build and the production nginx build (favicon path resolves under prod script-src 'self'/asset serving — served from public/, no CSP change expected).
• Any leftover vite.svg reference is removed.

Technical Notes

• Only file that needs changing is almost certainly src/frontend/index.html (favicon <link> + <title>); assets are already in public/icons/.
• Prefer the SVG favicon (type="image/svg+xml") for crispness, with a PNG fallback <link rel="alternate icon"> for browsers without SVG-favicon support.
• No document.title overrides were found in src/frontend/src, so the static <title> is authoritative; consider whether per-route titles are wanted (optional, out of scope for this fix).

[vybe]

/claim

[github-actions]

Claimed by @vybe. Label status-in-progress added.

Next steps:

1. Create branch: feature/1416-<short-slug>
2. Implement the feature
3. Open a PR with Fixes #1416