fix(look-at): build dynamic multimodal fallback chain

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-opencode)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

src/tools/look-at/multimodal-fallback-chain.ts

@@ -0,0 +1,49 @@
+import type { FallbackEntry } from "../../shared/model-requirements"
+import { AGENT_MODEL_REQUIREMENTS } from "../../shared/model-requirements"
+import type { VisionCapableModel } from "../../plugin-state"
+
+const MULTIMODAL_LOOKER_REQUIREMENT = AGENT_MODEL_REQUIREMENTS["multimodal-looker"]
+
+function getFullModelKey(providerID: string, modelID: string): string {
+  return `${providerID}/${modelID}`
+}
+
+export function isHardcodedMultimodalFallbackModel(model: VisionCapableModel): boolean {
+  return MULTIMODAL_LOOKER_REQUIREMENT.fallbackChain.some((entry) =>
+    entry.providers.some((providerID) =>
+      getFullModelKey(providerID, entry.model) === getFullModelKey(model.providerID, model.modelID),
+    ),
+  )
+}
+
+export function buildMultimodalLookerFallbackChain(
+  visionCapableModels: VisionCapableModel[],
+): FallbackEntry[] {
+  const seen = new Set<string>()
+  const fallbackChain: FallbackEntry[] = []
+
+  for (const visionCapableModel of visionCapableModels) {
+    const key = getFullModelKey(visionCapableModel.providerID, visionCapableModel.modelID)
+    if (seen.has(key)) continue
+
+    seen.add(key)
+    fallbackChain.push({
+      providers: [visionCapableModel.providerID],
+      model: visionCapableModel.modelID,
+    })
+  }
+
+  for (const entry of MULTIMODAL_LOOKER_REQUIREMENT.fallbackChain) {
+    const providerModelKeys = entry.providers.map((providerID) =>
+      getFullModelKey(providerID, entry.model),
+    )
+    if (providerModelKeys.every((key) => seen.has(key))) {
+      continue
+    }
+
+    providerModelKeys.forEach((key) => seen.add(key))
+    fallbackChain.push(entry)
+  }
+
+  return fallbackChain
+}