feat(acp): add owner broadcast routing

[koltyj]

Summary

• add an owner-broadcast ACP subscription mode
• broadcast an owner's untagged messages to every owned agent
• keep explicit agent mentions exclusive to the tagged agents
• include stream messages, forum posts, forum comments, approvals, and reminders by default
• document the mode and its environment setting

Validation

• bin/just ci
• ACP routing tests cover untagged owner messages, targeted agents in both tag orders, human recipients, lookup failures, non-owner messages, and forum kinds

Originating Buzz channel: 7a80f7af-3bec-4e17-a4ee-9f006a6eeac8

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Treat a missing agent profile as unresolved

When an owner explicitly targets a newly created agent whose kind:0 profile has not propagated yet, a successful empty query is not proof that the pubkey belongs to a human. Returning Some(false) here causes owner_broadcast_allows to continue broad delivery, so every older agent can execute a message intended exclusively for the new agent; the negative result is also cached for the process lifetime. Treat an empty or not-yet-attested profile as unresolved (None) or otherwise revalidate it before broadening delivery.

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