docs: handoff — trim Current state, move full-eval debt to ROADMAP, record SSH-input + CSRF conventions

- AGENTS.md: rewrite Current state lean for v0.19.0:0; drop the now-completed
  full-eval triage block (history lives in git log + EVALUATION.md).
- docs/guides/fastapi-image.md: add two durable conventions — user values
  crossing into SSH must go through shellsafe; new endpoints and the
  csrf_guard exempt-prefix rule.
- ROADMAP.md: park the remaining non-blocking P2/P3 tech debt from the eval.

docs/guides/fastapi-image.md

@@ -30,6 +30,8 @@ No pytest harness — each suite is a standalone script run with the `image/.ven
 
 - Pydantic request models go at **module scope**, never inside a `build_router()` body (FastAPI silently 422s otherwise).
 - New external-facing endpoints get documented in `docs/` (`AUDIO_API.md`, `EMBEDDINGS.md`, `REDACTION_GATEWAY.md`) and noted in release notes.
+- **SSH-input safety:** any user-supplied value that reaches an SSH command on the Sparks MUST go through `app/shellsafe.py` — validate against a whitelist at the API boundary, then `quote_arg`/`quote_args` (`shlex.quote`) at the sink. Never raw f-string a user value into a command string. Existing sinks: `models.build_launch_command`, `download`, `nim`, `services`; `disk.py` keeps its own `_SAFE_DIRNAME` because it needs `$HOME` to expand server-side. The vLLM pre-flight (`validate.py`) relies on `shlex.split` cleanly reversing this quoting — preserve that invariant.
+- **CSRF / same-origin:** state-mutating *control* endpoints are guarded by the `csrf_guard` middleware in `server.py` (rejects requests whose `Origin`/`Referer` host ≠ the served host). A new endpoint meant to be called **cross-origin by downstream apps** (a proxy/data endpoint) must be added to `_CSRF_EXEMPT_PREFIXES`, or browser POSTs from those apps will 403. No app-layer token auth by design (LAN/VPN-only; would break consumers).
 
 ## Layout