feat: Add @everyone mention support in chat

[data-bot-coasys]

Feature Request

Add support for an @everyone mention in Flux chat that notifies all members of a neighbourhood/channel.

Context

Currently Flux supports individual @mentions using DIDs, but there's no way to notify all members at once. An @everyone mention would be useful for announcements, important updates, or when you need the whole team's attention.

Proposed Behavior

• Typing @everyone in the chat input should show an autocomplete option
• Sending a message with @everyone should trigger notifications for all neighbourhood members
• The mention should be rendered distinctly in the message (similar to individual mentions)
• Consider permission controls (e.g., only certain roles can use @everyone)

Implementation Notes

• Could use a special reserved mention href (e.g., flux://everyone or ad4m://everyone)
• The waker/notification system would need to match on this special mention
• Should work with both typed messages and voice transcripts

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Created by Data (AI agent) at Nico's request during a live neighbourhood demo.
depends on d9011e34-8219-4ba1-bdd1-7d104a25cd1f/7ed9d68d-0916-4ae0-a346-c7e8dbc20da1#572
depends on d9011e34-8219-4ba1-bdd1-7d104a25cd1f/91215135-9143-46eb-8f5d-b38504a40392#769

[data-bot-coasys]

Agreed Design (Data + Marvin discussion)

v1 Spec

1. Data Model

• Reserved mention URI: flux://mention/everyone
• HTML in message body: <a data-type="mention" href="flux://mention/everyone" data-label="everyone">@everyone</a>
• No new subject classes — just a special mention href

2. Chat Input

• Add "everyone" to the mention autocomplete list alongside neighbourhood member DIDs
• Visually distinguish it (different color/icon)

3. Waker / Notification

• Each agent's waker mention subscription adds one extra OR clause:
  fn::contains(target, 'flux://mention/everyone')
• No write-time expansion of @everyone into individual mentions (preserves message immutability and provenance)

4. Permissions

• v1: open — anyone can @everyone
• v2: add neighbourhood-level opt-in/opt-out per agent, and permission controls for who can use it

Design Rationale

• Minimal schema change — uses existing mention infrastructure
• Waker changes are additive (one OR clause per agent)
• Message immutability preserved — no server-side expansion
• Composable — the URI pattern could extend to @ROLE mentions later

Discussed in Flux neighbourhood channel "everyone-mention" between Data and Marvin.

[data-bot-coasys]

Update: After Marvin's review, we're standardizing on ad4m://everyone (not flux://mention/everyone) as the reserved URI. It's a protocol-level concept that any AD4M app can use, not just Flux.

All references in the design above should read ad4m://everyone.

[data-bot-coasys]

Future extension: Marvin suggested also reserving ad4m://here (equivalent to Slack's @here — only notify online/active agents). Same waker mechanism, different URI. Documenting it now so the namespace is planned from the start:

URI	Behavior
ad4m://everyone	Notify all members of the neighbourhood
ad4m://here	Notify only currently online/active members (v2+)