fix(model-resolver): return variant from fallback chain, handle model name normalization

- Add variant to ModelResolutionResult return type
- Return variant from matched fallback entry
- Add normalizeModelName() for Claude model hyphen/period differences
- Add transformModelForProvider() for github-copilot model names
- Update delegate-task to use resolved variant (user config takes priority)
- Fix test expectations for new fallback behavior

src/shared/model-resolver.ts

@@ -16,6 +16,7 @@ export type ModelSource =
 export type ModelResolutionResult = {
 	model: string
 	source: ModelSource
+	variant?: string
 }
 
 export type ExtendedModelResolutionInput = {
@@ -57,8 +58,8 @@ export function resolveModelWithFallback(
 				const fullModel = `${provider}/${entry.model}`
 				const match = fuzzyMatchModel(fullModel, availableModels, [provider])
 				if (match) {
-					log("Model resolved via fallback chain (availability confirmed)", { provider, model: entry.model, match })
-					return { model: match, source: "provider-fallback" }
+					log("Model resolved via fallback chain (availability confirmed)", { provider, model: entry.model, match, variant: entry.variant })
+					return { model: match, source: "provider-fallback", variant: entry.variant }
 				}
 			}
 		}
@@ -68,8 +69,8 @@ export function resolveModelWithFallback(
 		const firstEntry = fallbackChain[0]
 		if (firstEntry.providers.length > 0) {
 			const fallbackModel = `${firstEntry.providers[0]}/${firstEntry.model}`
-			log("Model resolved via fallback chain first entry (no availability match)", { model: fallbackModel })
-			return { model: fallbackModel, source: "provider-fallback" }
+			log("Model resolved via fallback chain first entry (no availability match)", { model: fallbackModel, variant: firstEntry.variant })
+			return { model: fallbackModel, source: "provider-fallback", variant: firstEntry.variant }
 		}
 	}