Multi-device: mention picker cannot reach remotely-hosted agents (owner-only unhandled, directory never updated, replies never p-tag authors) #4535

Setup: one user, two devices, same key. Device A's Buzz Desktop hosts the agents; device B is a pure client (same identity imported). Community = the user + their agents.

Symptom: on device B the @ picker offers no agents at all (only the user's own name). Plain-typed @NAMEs and thread replies publish but notify nobody, and agents wake only on p-tagged events (buzz-acp shipped default subscribe = "mentions" with require_mention = true, crates/buzz-acp/src/config.rs) — so device B has no channel path to reach any agent. (Deployments can override via BUZZ_ACP_SUBSCRIBE / BUZZ_ACP_NO_MENTION_FILTER; this issue describes the code default.)

Defect 1 — eligibility: desktop/src/features/agents/lib/agentAutocompleteEligibility.ts — relayAgentIsSharedWithUser() handles respondTo allowlist/anyone only; no owner-only branch, and RelayAgent carries no ownerPubkey (the kind:10100 card has no owner field), so owner-only agents are hidden even from their own owner on every non-hosting device.

Defect 2 — settings cannot propagate: Desktop saves respond-to edits into the owner-side kind:30177 managed-agent record, but the picker reads kind:10100 cards — and repo-wide the only kind:10100 writer is buzz-cli channels set-add-policy (content = {"channel_add_policy"} only). No code path ever writes or updates respond_to/channel_ids on the card, so switching an agent to Anyone/Selected-people can never make it picker-visible on another device.

Defect 3 — replies never p-tag the parent author: thread_tags() in crates/buzz-sdk/src/builders.rs emits only NIP-10 e-tags; Desktop's messageMentionPubkeys.ts states "Stream messages notify only explicit mentions." So "reply to a message to reach its author" is impossible for every client, which removes the natural fallback for defects 1-2.

Defect 4 — misleading dialog copy: the Selected-people edit dialog tells the owner "you don't need to add yourself" (desktop/src/features/agents/ui/RespondToField.tsx:334), but picker eligibility checks the literal published allowlist — following the dialog makes the fix silently fail even once defect 2 is repaired.

Suggested direction: publish ownerPubkey on the directory card and add an owner-only branch; republish (or relay-derive) directory data when respond-to changes, or let a client read its own owner's kind:30177 records; p-tag the parent author on replies per NIP-10; fix the dialog copy.

Impact: every multi-device user; becomes fleet-wide once agents run headless/remote (VPS), where every client is a non-hosting device.