feat: add API key and custom provider configuration (#4)

* feat: add API key and custom provider configuration

Previously, model setup only offered OAuth login. This adds:

- API key configuration for 17 built-in providers (OpenAI, Anthropic,
  Google, Mistral, Groq, xAI, OpenRouter, etc.)
- Custom provider setup via models.json (for Ollama, vLLM, LM Studio,
  proxies, or any OpenAI/Anthropic/Google-compatible endpoint)
- Interactive prompts with smart defaults and auto-detection of models
- Verification flow that probes endpoints and provides actionable tips
- Doctor diagnostics for models.json path and missing apiKey warnings
- Dev environment fallback for running without dist/ build artifacts
- Unified auth flow: `feynman model login` now offers both API key
  and OAuth options (OAuth-only when a specific provider is given)

New files:
- src/model/models-json.ts: Read/write models.json with proper merging
- src/model/registry.ts: Centralized ModelRegistry creation with modelsJsonPath
- tests/models-json.test.ts: Unit tests for provider config upsert

* fix: harden runtime env and custom provider auth

---------

Co-authored-by: Advait Paliwal <advaitspaliwal@gmail.com>

src/setup/doctor.ts

@@ -1,6 +1,7 @@
-import { AuthStorage, ModelRegistry } from "@mariozechner/pi-coding-agent";
 import { getUserName as getAlphaUserName, isLoggedIn as isAlphaLoggedIn } from "@companion-ai/alpha-hub/lib";
 
+import { readFileSync } from "node:fs";
+
 import { formatPiWebAccessDoctorLines, getPiWebAccessStatus } from "../pi/web-access.js";
 import { BROWSER_FALLBACK_PATHS, PANDOC_FALLBACK_PATHS, resolveExecutable } from "../system/executables.js";
 import { readJson } from "../pi/settings.js";
@@ -8,6 +9,30 @@ import { validatePiInstallation } from "../pi/runtime.js";
 import { printInfo, printPanel, printSection } from "../ui/terminal.js";
 import { getCurrentModelSpec } from "../model/commands.js";
 import { buildModelStatusSnapshotFromRecords, getAvailableModelRecords, getSupportedModelRecords } from "../model/catalog.js";
+import { createModelRegistry, getModelsJsonPath } from "../model/registry.js";
+
+function findProvidersMissingApiKey(modelsJsonPath: string): string[] {
+	try {
+		const raw = readFileSync(modelsJsonPath, "utf8").trim();
+		if (!raw) return [];
+		const parsed = JSON.parse(raw) as any;
+		const providers = parsed?.providers;
+		if (!providers || typeof providers !== "object") return [];
+		const missing: string[] = [];
+		for (const [providerId, config] of Object.entries(providers as Record<string, unknown>)) {
+			if (!config || typeof config !== "object") continue;
+			const models = (config as any).models;
+			if (!Array.isArray(models) || models.length === 0) continue;
+			const apiKey = (config as any).apiKey;
+			if (typeof apiKey !== "string" || apiKey.trim().length === 0) {
+				missing.push(providerId);
+			}
+		}
+		return missing;
+	} catch {
+		return [];
+	}
+}
 
 export type DoctorOptions = {
 	settingsPath: string;
@@ -104,7 +129,7 @@ export function runStatus(options: DoctorOptions): void {
 
 export function runDoctor(options: DoctorOptions): void {
 	const settings = readJson(options.settingsPath);
-	const modelRegistry = new ModelRegistry(AuthStorage.create(options.authPath));
+	const modelRegistry = createModelRegistry(options.authPath);
 	const availableModels = modelRegistry.getAvailable();
 	const pandocPath = resolveExecutable("pandoc", PANDOC_FALLBACK_PATHS);
 	const browserPath = process.env.PUPPETEER_EXECUTABLE_PATH ?? resolveExecutable("google-chrome", BROWSER_FALLBACK_PATHS);
@@ -144,6 +169,21 @@ export function runDoctor(options: DoctorOptions): void {
 	if (modelStatus.recommendedModelReason) {
 		console.log(`  why: ${modelStatus.recommendedModelReason}`);
 	}
+	const modelsError = modelRegistry.getError();
+	if (modelsError) {
+		console.log("models.json: error");
+		for (const line of modelsError.split("\n")) {
+			console.log(`  ${line}`);
+		}
+	} else {
+		const modelsJsonPath = getModelsJsonPath(options.authPath);
+		console.log(`models.json: ${modelsJsonPath}`);
+		const missingApiKeyProviders = findProvidersMissingApiKey(modelsJsonPath);
+		if (missingApiKeyProviders.length > 0) {
+			console.log(`  warning: provider(s) missing apiKey: ${missingApiKeyProviders.join(", ")}`);
+			console.log("  note: custom providers with a models[] list need apiKey in models.json to be available.");
+		}
+	}
 	console.log(`pandoc: ${pandocPath ?? "missing"}`);
 	console.log(`browser preview runtime: ${browserPath ?? "missing"}`);
 	for (const line of formatPiWebAccessDoctorLines()) {