Update Hyperchannel for Sockethub activity-streams refactor (blocked on sockethub/sockethub#1088)

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Summary

Sockethub PR #1088 removes the @sockethub/activity-streams package and the server-side activity-object shorthand protocol. Activity stream normalization and development-time property linting move into @sockethub/schemas.

Hyperchannel must be updated and verified against a Sockethub build from that branch (or the release cut from it) before #1088 can merge.

What changed in Sockethub

• @sockethub/activity-streams deleted
• Server activity-object socket handler removed
• expand-activity-stream / create-activity-object middleware replaced by normalize-activity-stream
• No process-wide object store; each client gets a private stream processor
• Platform object properties (e.g. xmpp:replace, xmpp:stanza-id) are derived from platform message schemas after ready()
• packageConfig and the activity-streams server config section removed

Current Hyperchannel state

Hyperchannel already does several things the new API expects:

• Loads the browser client from the Sockethub server and calls await client.ready() before use
• Uses client.contextFor('irc' | 'xmpp') after initialization
• Sends actor objects as { id, type: 'person' } rather than bare string refs
• Does not appear to use the removed activity-object protocol

However, compatibility has not been verified end-to-end against the refactored Sockethub, and some areas likely need attention.

Work items

1. Update local Sockethub config

sockethub.config.json still contains an activity-streams section:

"activity-streams": {
  "opts": {
    "specialObjs": [ "credentials" ]
  }
}