Adds two API server endpoints for external UIs and orchestrators:
- GET /v1/capabilities — machine-readable feature discovery so clients
can detect which Runs API / SSE / auth features this Hermes version
supports before depending on them.
- GET /v1/runs/{run_id} — pollable run status so dashboards can check
queued/running/completed/failed/cancelled/stopping state without
holding an SSE connection open.
Also moves request validation ahead of run allocation so invalid
payloads no longer leave orphaned entries in _run_streams waiting for
the TTL sweep.
task_id is intentionally kept as "default" for the Runs API to
preserve the shared-sandbox model used by CLI, gateway, and the
existing _run_agent_with_callbacks path. session_id is surfaced in
run status for external-UI correlation only.
Salvage of PR #17085 by @Magaav.
Add ability to interrupt a running agent via the runs API. Previously
/v1/runs could start a run and subscribe to events, but there was no
way to cancel it. The new endpoint stores agent and task references
during execution, calls agent.interrupt() to stop LLM calls, then
cancels the asyncio task.
Includes 15 tests covering start, events, and stop scenarios.
