fix(loki): vision is a provider chain, not a pinned model that rots

[catomean]

The bug

Every screenshot attached to Loki has been failing. GROQ_VISION_MODEL pinned meta-llama/llama-4-scout-17b-16e-instruct, which is decommissioned — 404 — and Groq now serves no vision model at all on this account.

Found while probing models for the tool loop (#214), not by anyone using the feature. That's the part worth fixing.

Why a chain, not a new pin

This is the fourth pinned-free-model rot in this fleet. A single pinned free model is a scheduled outage, so this gets the class treatment:

File	Role
config/vision-models.ts	A chain across providers, tried in order. Entries are OpenAI-compatible, so adding a provider is a row in a table, not a new client. Groq keeps a seat with no default model so restoring one later is one string.
lib/vision.ts	Walks the chain; first real answer wins.
scripts/probe-models.ts	Now probes both halves — chat tool-calling AND vision, with a real image. npm run probe:models.

"Real answer" is load-bearing. nvidia/nemotron-nano-12b-v2-vl returns HTTP 200 with empty content, which a naive client reports as a successful analysis of nothing — reading to the user as "nothing notable in your screenshot" rather than as a failure. Empty is treated as a dead link and the chain continues.

Verified live

Against a solid-colour test image:

✓ google/gemma-4-26b-a4b-it:free   200, correctly answered "Red"
⚠ google/gemma-4-31b-it:free       429 rate limited  → kept as fallback
✗ nvidia/nemotron-nano-12b-v2-vl   200 but empty     → excluded

End-to-end through the new chain:

Vision chain (2 usable link(s)):
  ✓ openrouter/google/gemma-4-26b-a4b-it:free → answered: Red

Credential

FleetCrown had no vision-capable credential at all. It now shares orangecat's OPENROUTER_API_KEY, appended to /opt/fleetcrown/app/.env on the box (backed up first). deploy.sh bootstraps that file into shared/ on the next release, so it survives.

Cleanup

Retires callGroqVision + GROQ_VISION_MODEL — one caller, now on the chain. Leaving a dead constant behind is how the next person re-pins a dead model.

The analysis block now names the model that read the image: it's the one part of a Loki turn not grounded in FleetCrown's records, and saying so keeps it from blending into the cited answer around it.

65/65 unit files pass, tsc clean, 0 lint errors.

🤖 Generated with Claude Code