feat(desktop): auto-enable huddle transcription for agents

[johnmatthewtennant]

Context

Before this change, every huddle initialized with transcription off. Joining or adding an agent did not enable it, so the agent could not receive spoken conversation until a person clicked the transcript control. Starting a huddle from an agent DM could also omit that agent, and adding an agent who already belonged to the parent channel could attempt an unnecessary role change and show a warning.

Agent detection uses authoritative huddle membership. A participant counts as an agent when the ephemeral membership identifies it with the bot role, or when the existing agent identity model identifies the participant in an agent DM.

Summary

Buzz now enables transcription once when the first authoritative agent is present. After that initial automatic action, explicit user control is authoritative: manual ON or OFF survives membership refreshes, reconnects, and UI remounts. Removing the last agent does not change the current transcription state.

Agent-DM huddles enroll the agent automatically. Adding an agent who already belongs to the parent channel preserves the existing parent role and completes without a role-mutation warning.

Scenario	Before	With this change
First authoritative agent joins or is hydrated	Transcription stays off	Transcription turns on once
User explicitly turns transcription on or off	Manual control exists without an agent policy	The explicit choice suppresses later automatic changes
Last agent leaves	No defined agent-presence behavior	The current transcription state remains unchanged
Huddle starts from an agent DM	The agent can be omitted	The known agent is enrolled automatically
Added agent already belongs to the parent channel	Buzz can attempt a role rewrite and warn	Existing parent membership and role are preserved
Transcription is active	The control is not visually distinct	The control is highlighted and exposes aria-pressed=true

Changes

• Derive agent presence from authoritative bot-role huddle membership and known agent-DM identity.
• Apply the one-time auto-enable rule during create, join, membership hydration, reconnect, pipeline startup, and local agent addition.
• Preserve explicit user state and use huddle-generation guards so stale asynchronous work cannot alter a replacement huddle.
• Keep backend and React transcription state synchronized, with a visible and accessible active control.
• Enroll known agent-DM participants and make parent-channel membership updates idempotent.
• Cover hydration ordering, reconnects, remounts, explicit OFF, last-agent removal, DM enrollment, existing membership, and active styling.

Related issue

None found.

Testing

Manual validation in pending-seed confirmed the product contract:

1. Started a huddle from the owned, running Fizz agent DM.
2. Confirmed the authoritative roster contained the human and Fizz as an agent.
3. Confirmed transcription enabled without clicking the control: Stop transcript, aria-pressed=true, with the highlighted active background.
4. Turned transcription off and confirmed Start transcript, aria-pressed=false remained stable.
5. Removed Fizz while transcription was off and confirmed the state stayed off.
6. Left the huddle cleanly.

Screenshots

The same control has distinct active and inactive states.

Reviewer-reproducible examples

From a fresh checkout:

pnpm --dir desktop build:e2e
pnpm --dir desktop exec playwright test tests/e2e/huddle-transcription.spec.ts --project=smoke
pnpm --dir desktop exec playwright test tests/e2e/mentions.spec.ts --project=smoke --grep "system agent profile exposes owned agent actions|system agent avatar exposes owned agent actions|owned bot profile exposes message and huddle actions|owned agent mention profile exposes message and huddle actions"

The huddle scenario exercises initial authoritative hydration, exactly one automatic enable, explicit OFF persistence, unchanged state after last-agent removal, newer events winning over delayed hydration, agent-DM enrollment, and idempotent parent membership. It also asserts aria-pressed and distinct computed active styling.

[johnmatthewtennant]

🤖 ## Active transcription

The transcript control uses the highlighted active state and reports pressed/on.

Inactive transcription

After explicit OFF, the control returns to the dark inactive state and reports pressed/off.