Register Dr.XAS (drxas) — XANES connectivity/workflow test agent

[JingTang-Enid]

Adds registry/agents/drxas-input-sender.yaml.

Minimal A2A test agent (connectivity + workflow validation) hosted on drxas.xray.aps.anl.gov. On each message/send it grabs a random XANES .input file and returns it as a job (text part + A2A artifact).

• protocol: a2a
• card_url: https://drxas.xray.aps.anl.gov:8443/.well-known/agent-card.json
• auth: bearer (token exchanged out of band)
• skill: send-xanes-input
• status: pending

⚠️ Note: the endpoint currently serves TLS with a self-signed cert (no sudo / ACME egress on the host). Can swap in a proper cert if go-live requires it.

Maintainer: @JingTang-Enid

[zhenghh04]

Requesting more detail before merge (safety/community review)

The registry entry is schema-valid and passes CI, but for a new agent joining shared Trinity rooms we'd like a bit more than the one-line description before this goes live. Could you answer:

1. Behavior. Beyond "grabs a random XANES .input file" — does Dr.XAS read/react to the room transcript at all, or does it ignore incoming text entirely and just return a file regardless of prompt? (If it truly ignores the transcript, that's actually a nice safety property — please confirm.)
2. Example interaction. 2–3 example prompts a room participant might send it, and the exact expected response for each (including what an unexpected input, like an empty room or a hostile/off-topic prompt, produces).
3. Data provenance. Where do the .input files come from — real experimental/beamline data, synthetic, or public test fixtures? Is any of it unpublished/proprietary, and is there a risk in it being pasted into a shared room?
4. Abuse/rate limits. What happens if it's @mentioned rapidly or repeatedly — any rate limiting, or could a room flood it (or get flooded by it)?
5. Data handling. Does drxas.xray.aps.anl.gov log or retain the transcripts Trinity sends it? Per docs/security.md, transcripts may contain other participants' text, not just the caller's.
6. Failure mode. What does it return on a malformed request or when the input-file pool is empty/unavailable — a JSON-RPC error, or something else?

This isn't specific to Dr.XAS — it's the first "test agent" registration we've had, so answering this also helps us firm up docs/register-an-agent.md / the issue template with an explicit safety-interview section for future submissions.