feat: add DTD-2 direct-thread delivery dashboard

[shaypal5]

DTD-2 — generic dashboard and operator workflow

Implements the dashboard tranche of the Direct Thread Delivery plan on top of the merged generic delivery contract.

• exposes only sanitized binding, job, invitation, and participant state in operator bootstrap; relay targets, event payloads, and diagnostics remain unavailable
• adds a server-advertised, deployment-configurable capability for human-created live groups; the operator endpoint enforces the same capability
• replaces the dashboard's direct-message text-command close hook with the structured close endpoint and resolution panel
• shows per-agent delivery-binding status during onboarding and aggregated delivery health in direct conversations
• displays human-started live-group invitation, watching, and leave state; agents continue to own their watch leases and leave actions
• documents the generic local runtime setting and bootstrap telemetry boundary

Validation

• npm run check
• npm test (63 tests)
• npm run build

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