feat: check provider connectivity instead of specific model for hephaestus availability

Hephaestus now appears when any of its providers (openai, github-copilot, opencode) is
connected, rather than requiring the exact gpt-5.2-codex model. This allows users with
newer codex models (e.g., gpt-5.3-codex) to use Hephaestus without manual config overrides.

- Add requiresProvider field to ModelRequirement type
- Add isAnyProviderConnected() helper in model-availability
- Update hephaestus config from requiresModel to requiresProvider
- Update cli model-fallback to handle requiresProvider checks

src/shared/model-availability.ts

@@ -317,6 +317,35 @@ export function isAnyFallbackModelAvailable(
 	return false
 }
 
+export function isAnyProviderConnected(
+	providers: string[],
+	availableModels: Set<string>,
+): boolean {
+	if (availableModels.size > 0) {
+		const providerSet = new Set(providers)
+		for (const model of availableModels) {
+			const [provider] = model.split("/")
+			if (providerSet.has(provider)) {
+				log("[isAnyProviderConnected] found model from required provider", { provider, model })
+				return true
+			}
+		}
+	}
+
+	const connectedProviders = readConnectedProvidersCache()
+	if (connectedProviders) {
+		const connectedSet = new Set(connectedProviders)
+		for (const provider of providers) {
+			if (connectedSet.has(provider)) {
+				log("[isAnyProviderConnected] provider connected via cache", { provider })
+				return true
+			}
+		}
+	}
+
+	return false
+}
+
 export function __resetModelCache(): void {}
 
 export function isModelCacheAvailable(): boolean {

src/shared/model-requirements.test.ts

@@ -176,14 +176,15 @@ describe("AGENT_MODEL_REQUIREMENTS", () => {
     expect(primary.providers[0]).toBe("kimi-for-coding")
   })
 
-  test("hephaestus requires gpt-5.2-codex", () => {
+  test("hephaestus requires openai/github-copilot/opencode provider", () => {
     // #given - hephaestus agent requirement
     const hephaestus = AGENT_MODEL_REQUIREMENTS["hephaestus"]
 
     // #when - accessing hephaestus requirement
-    // #then - requiresModel is set to gpt-5.2-codex
+    // #then - requiresProvider is set to openai, github-copilot, opencode (not requiresModel)
     expect(hephaestus).toBeDefined()
-    expect(hephaestus.requiresModel).toBe("gpt-5.2-codex")
+    expect(hephaestus.requiresProvider).toEqual(["openai", "github-copilot", "opencode"])
+    expect(hephaestus.requiresModel).toBeUndefined()
   })
 
   test("all 10 builtin agents have valid fallbackChain arrays", () => {

src/shared/model-requirements.ts

@@ -9,6 +9,7 @@ export type ModelRequirement = {
   variant?: string // Default variant (used when entry doesn't specify one)
   requiresModel?: string // If set, only activates when this model is available (fuzzy match)
   requiresAnyModel?: boolean // If true, requires at least ONE model in fallbackChain to be available (or empty availability treated as unavailable)
+  requiresProvider?: string[] // If set, only activates when any of these providers is connected
 }
 
 export const AGENT_MODEL_REQUIREMENTS: Record<string, ModelRequirement> = {
@@ -27,7 +28,7 @@ export const AGENT_MODEL_REQUIREMENTS: Record<string, ModelRequirement> = {
     fallbackChain: [
       { providers: ["openai", "github-copilot", "opencode"], model: "gpt-5.2-codex", variant: "medium" },
     ],
-    requiresModel: "gpt-5.2-codex",
+    requiresProvider: ["openai", "github-copilot", "opencode"],
   },
   oracle: {
     fallbackChain: [