Activity tab: filter by client + resolve @pubkey references to names

[DocNR]

Verified still open against current source (build 102, 2026-08-10).

• Activity tab has no per-client filter. Filter chips only cover method/status (All / sign_event / connect / pending); there's no dropdown to narrow by connected client. Clave/Views/Activity/ActivityView.swift.
• Activity detail summaries show raw truncated hex for referenced pubkeys (e.g. "Reply to e:abc123de…abcd · @alice567…aaaa"). Resolving @<pubkey> to a display name would meaningfully improve scannability. Clave/Views/Activity/ActivityDetailView.swift:105. Needs a multi-keyed profile cache (today's cache is single-slot, account-scoped only) plus a privacy design call — querying relays with a batch of pubkeys leaks "this user is interested in these people" to the relay operator. Options: query only relays the user already uses, one-at-a-time fetches, or a user-controlled toggle. Worth checking whether @<pubkey> references show up often enough in real activity logs before investing here.

Source: internal backlog triage, 2026-08-10.