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/pi/launch.ts

@@ -7,11 +7,14 @@ import { ensureSupportedNodeVersion } from "../system/node-version.js";
 export async function launchPiChat(options: PiRuntimeOptions): Promise<void> {
 	ensureSupportedNodeVersion();
 
-	const { piCliPath, promisePolyfillPath } = resolvePiPaths(options.appRoot);
+	const { piCliPath, promisePolyfillPath, promisePolyfillSourcePath, tsxLoaderPath } = resolvePiPaths(options.appRoot);
 	if (!existsSync(piCliPath)) {
 		throw new Error(`Pi CLI not found: ${piCliPath}`);
 	}
-	if (!existsSync(promisePolyfillPath)) {
+
+	const useBuiltPolyfill = existsSync(promisePolyfillPath);
+	const useDevPolyfill = !useBuiltPolyfill && existsSync(promisePolyfillSourcePath) && existsSync(tsxLoaderPath);
+	if (!useBuiltPolyfill && !useDevPolyfill) {
 		throw new Error(`Promise polyfill not found: ${promisePolyfillPath}`);
 	}
 
@@ -19,7 +22,11 @@ export async function launchPiChat(options: PiRuntimeOptions): Promise<void> {
 		process.stdout.write("\x1b[2J\x1b[3J\x1b[H");
 	}
 
-	const child = spawn(process.execPath, ["--import", promisePolyfillPath, piCliPath, ...buildPiArgs(options)], {
+	const importArgs = useDevPolyfill
+		? ["--import", tsxLoaderPath, "--import", promisePolyfillSourcePath]
+		: ["--import", promisePolyfillPath];
+
+	const child = spawn(process.execPath, [...importArgs, piCliPath, ...buildPiArgs(options)], {
 		cwd: options.workingDir,
 		stdio: "inherit",
 		env: buildPiEnv(options),

src/pi/runtime.ts

@@ -25,6 +25,8 @@ export function resolvePiPaths(appRoot: string) {
 		piPackageRoot: resolve(appRoot, "node_modules", "@mariozechner", "pi-coding-agent"),
 		piCliPath: resolve(appRoot, "node_modules", "@mariozechner", "pi-coding-agent", "dist", "cli.js"),
 		promisePolyfillPath: resolve(appRoot, "dist", "system", "promise-polyfill.js"),
+		promisePolyfillSourcePath: resolve(appRoot, "src", "system", "promise-polyfill.ts"),
+		tsxLoaderPath: resolve(appRoot, "node_modules", "tsx", "dist", "loader.mjs"),
 		researchToolsPath: resolve(appRoot, "extensions", "research-tools.ts"),
 		promptTemplatePath: resolve(appRoot, "prompts"),
 		systemPromptPath: resolve(appRoot, ".feynman", "SYSTEM.md"),
@@ -38,7 +40,11 @@ export function validatePiInstallation(appRoot: string): string[] {
 	const missing: string[] = [];
 
 	if (!existsSync(paths.piCliPath)) missing.push(paths.piCliPath);
-	if (!existsSync(paths.promisePolyfillPath)) missing.push(paths.promisePolyfillPath);
+	if (!existsSync(paths.promisePolyfillPath)) {
+		// Dev fallback: allow running from source without `dist/` build artifacts.
+		const hasDevPolyfill = existsSync(paths.promisePolyfillSourcePath) && existsSync(paths.tsxLoaderPath);
+		if (!hasDevPolyfill) missing.push(paths.promisePolyfillPath);
+	}
 	if (!existsSync(paths.researchToolsPath)) missing.push(paths.researchToolsPath);
 	if (!existsSync(paths.promptTemplatePath)) missing.push(paths.promptTemplatePath);
 
@@ -94,6 +100,8 @@ export function buildPiEnv(options: PiRuntimeOptions): NodeJS.ProcessEnv {
 		FEYNMAN_NODE_EXECUTABLE: process.execPath,
 		FEYNMAN_BIN_PATH: resolve(options.appRoot, "bin", "feynman.js"),
 		FEYNMAN_NPM_PREFIX: feynmanNpmPrefixPath,
+		// Ensure the Pi child process uses Feynman's agent dir for auth/models/settings.
+		PI_CODING_AGENT_DIR: options.feynmanAgentDir,
 		PANDOC_PATH: process.env.PANDOC_PATH ?? resolveExecutable("pandoc", PANDOC_FALLBACK_PATHS),
 		PI_HARDWARE_CURSOR: process.env.PI_HARDWARE_CURSOR ?? "1",
 		PI_SKIP_VERSION_CHECK: process.env.PI_SKIP_VERSION_CHECK ?? "1",

src/pi/settings.ts

@@ -1,9 +1,10 @@
 import { existsSync, mkdirSync, readFileSync, writeFileSync } from "node:fs";
 import { dirname } from "node:path";
 
-import { AuthStorage, ModelRegistry, type PackageSource } from "@mariozechner/pi-coding-agent";
+import { ModelRegistry, type PackageSource } from "@mariozechner/pi-coding-agent";
 
 import { CORE_PACKAGE_SOURCES, shouldPruneLegacyDefaultPackages } from "./package-presets.js";
+import { createModelRegistry } from "../model/registry.js";
 
 export type ThinkingLevel = "off" | "minimal" | "low" | "medium" | "high" | "xhigh";
 
@@ -115,8 +116,7 @@ export function normalizeFeynmanSettings(
 		settings.packages = [...CORE_PACKAGE_SOURCES];
 	}
 
-	const authStorage = AuthStorage.create(authPath);
-	const modelRegistry = new ModelRegistry(authStorage);
+	const modelRegistry = createModelRegistry(authPath);
 	const availableModels = modelRegistry.getAvailable().map((model) => ({
 		provider: model.provider,
 		id: model.id,