fix: handle both string[] and object[] formats in provider-models cache

Category delegation fails when provider-models.json contains model objects
with metadata (id, provider, context, output) instead of plain strings.
Line 196 in model-availability.ts assumes string[] format, causing:
  - Object concatenation: `${providerId}/${modelId}` becomes "ollama/[object Object]"
  - Empty availableModels Set passed to resolveModelPipeline()
  - Error: "Model not configured for category"

This is the root cause of issue #1508 where delegate_task(category='quick')
fails despite direct agent routing (delegate_task(subagent_type='explore'))
working correctly.

Changes:
- model-availability.ts: Add type check to handle both string and object formats
- connected-providers-cache.ts: Update ProviderModelsCache interface to accept both formats
- model-availability.test.ts: Add 4 test cases for object[] format handling

Direct agent routing bypasses fetchAvailableModels() entirely, explaining why
it works while category routing fails. This fix enables category delegation
to work with manually-populated Ollama model caches.

Fixes #1508

src/shared/model-availability.ts

@@ -187,16 +187,23 @@ export async function fetchAvailableModels(
 		if (providerCount === 0) {
 			log("[fetchAvailableModels] provider-models cache empty, falling back to models.json")
 		} else {
-			log("[fetchAvailableModels] using provider-models cache (whitelist-filtered)")
-			
-			for (const [providerId, modelIds] of Object.entries(providerModelsCache.models)) {
-				if (!connectedSet.has(providerId)) {
-					continue
-				}
-				for (const modelId of modelIds) {
+		log("[fetchAvailableModels] using provider-models cache (whitelist-filtered)")
+		
+		for (const [providerId, modelIds] of Object.entries(providerModelsCache.models)) {
+			if (!connectedSet.has(providerId)) {
+				continue
+			}
+			for (const modelItem of modelIds) {
+				// Handle both string[] (legacy) and object[] (with metadata) formats
+				const modelId = typeof modelItem === 'string' 
+					? modelItem 
+					: (modelItem as any)?.id
+				
+				if (modelId) {
 					modelSet.add(`${providerId}/${modelId}`)
 				}
 			}
+		}
 
 			log("[fetchAvailableModels] parsed from provider-models cache", {
 				count: modelSet.size,