feat: add "Anthropic — via Claude CLI" as a first-class provider

Replaces the stray useClaudeCli settings checkbox + onboarding question
with a proper provider-card UX. The card lives next to OAuth + API-key
cards in onboarding and settings, with Enable/Disable + Test actions.

Backend:
 - Vendors rchern/pi-claude-cli@0.3.1 as packages/pi-claude-cli
   (MIT, attribution in UPSTREAM.md). Lets us bump peer-dep on
   pi-coding-agent in lockstep with Fusion (upstream pinned ^0.52.0
   vs ours ^0.62.0) and fix bugs without waiting on upstream.
 - Adds @fusion/pi-claude-cli as a workspace dep of @runfusion/fusion
   so users don't have to `npm install -g pi-claude-cli` manually.
 - serve/daemon/dashboard conditionally load the extension via
   discoverAndLoadExtensions() when GlobalSettings.useClaudeCli is on;
   no side-effects on user ~/.fusion/agent/settings.json.
 - New GET /api/providers/claude-cli/status: claude --version probe
   + toggle state + cached extension resolution.
 - New POST /api/auth/claude-cli: flips useClaudeCli, refuses if the
   claude binary is missing, fires the existing skill-backfill hook.
 - /api/auth/status now injects a synthetic {id:"claude-cli", type:"cli"}
   provider entry so onboarding + settings see a consistent list.

Frontend:
 - New ClaudeCliProviderCard component shared between ModelOnboardingModal
   and SettingsModal's Authentication section.
 - New AuthProvider.type = "cli" variant.
 - Removed the old "Route AI calls through the Claude CLI" checkbox from
   Global Models settings and the opt-in step from the onboarding wizard.
 - ProviderIcon gets a composite Anthropic-mark-plus-terminal glyph for
   the claude-cli provider id.

Tests:
 - 8 unit tests for extension resolution (@fusion/pi-claude-cli is
   workspace-linked so these run in-tree).
 - 2 unit tests for the binary probe.
 - Existing /auth/status tests filter out the new synthetic entry so
   they keep asserting structural OAuth/API-key behavior in isolation.
 - The vendored package's own 296 tests still pass unchanged.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

packages/pi-claude-cli/src/process-manager.ts

@@ -0,0 +1,218 @@
+/**
+ * Process manager for spawning and managing Claude CLI subprocesses.
+ *
+ * Handles subprocess lifecycle: spawn with correct CLI flags, write NDJSON
+ * messages to stdin, force-kill after result (CLI hangs bug), and stderr capture.
+ * Also provides startup validation for CLI presence and authentication.
+ */
+
+import spawn from "cross-spawn";
+import { execSync } from "node:child_process";
+import { writeFileSync, unlinkSync } from "node:fs";
+import { join } from "node:path";
+import { tmpdir } from "node:os";
+import type { ChildProcess } from "node:child_process";
+
+/**
+ * Spawn a Claude CLI subprocess with all required flags for stream-json communication.
+ *
+ * @param modelId - The model ID to pass via --model flag
+ * @param systemPrompt - Optional system prompt appended via --append-system-prompt
+ * @param options - Optional cwd, AbortSignal, and effort level
+ * @returns The spawned ChildProcess with piped stdin/stdout/stderr
+ */
+export function spawnClaude(
+  modelId: string,
+  systemPrompt?: string,
+  options?: {
+    cwd?: string;
+    signal?: AbortSignal;
+    effort?: string;
+    mcpConfigPath?: string;
+    resumeSessionId?: string;
+    newSessionId?: string;
+  },
+): ChildProcess {
+  const args = [
+    "-p",
+    "--input-format",
+    "stream-json",
+    "--output-format",
+    "stream-json",
+    "--verbose",
+    "--include-partial-messages",
+    "--model",
+    modelId,
+    "--permission-prompt-tool",
+    "stdio",
+  ];
+
+  if (options?.resumeSessionId) {
+    // Resume an existing session — CLI loads prior conversation from disk
+    args.push("--resume", options.resumeSessionId);
+  } else if (options?.newSessionId) {
+    // First turn: create session with this ID so subsequent turns can --resume it
+    args.push("--session-id", options.newSessionId);
+  }
+
+  if (systemPrompt) {
+    // Write system prompt to a temp file to avoid ENAMETOOLONG on Windows.
+    // Claude CLI's --append-system-prompt accepts a file path or literal text.
+    const tmpFile = join(
+      tmpdir(),
+      `pi-claude-cli-sysprompt-${process.pid}.txt`,
+    );
+    writeFileSync(tmpFile, systemPrompt, "utf-8");
+    args.push("--append-system-prompt", tmpFile);
+  }
+
+  if (options?.effort) {
+    args.push("--effort", options.effort);
+  }
+
+  if (options?.mcpConfigPath) {
+    args.push("--mcp-config", options.mcpConfigPath);
+  }
+
+  const proc = spawn("claude", args, {
+    stdio: ["pipe", "pipe", "pipe"],
+    cwd: options?.cwd ?? process.cwd(),
+  });
+
+  return proc as ChildProcess;
+}
+
+/**
+ * Clean up the temp system prompt file created by spawnClaude.
+ * Safe to call multiple times or when no file exists.
+ */
+export function cleanupSystemPromptFile(): void {
+  try {
+    unlinkSync(join(tmpdir(), `pi-claude-cli-sysprompt-${process.pid}.txt`));
+  } catch {
+    // File doesn't exist or already deleted — ignore
+  }
+}
+
+/**
+ * Write a user message to the subprocess stdin as NDJSON.
+ * Does NOT call stdin.end() -- stdin stays open for control_response in Phase 2.
+ *
+ * Accepts both string (text-only prompt) and array (ContentBlock[] with images)
+ * content. JSON.stringify handles both natively. The stream-json protocol
+ * supports either format in the content field.
+ *
+ * @param proc - The Claude subprocess
+ * @param prompt - The prompt text or ContentBlock[] to send
+ */
+export function writeUserMessage(
+  proc: ChildProcess,
+  prompt: string | any[],
+): void {
+  const message = {
+    type: "user",
+    message: {
+      role: "user",
+      content: prompt,
+    },
+  };
+  proc.stdin!.write(JSON.stringify(message) + "\n");
+}
+
+/**
+ * Force-kill a subprocess immediately via SIGKILL.
+ * No-ops if the process is already dead (killed or exited).
+ * Cross-platform safe: Node.js treats SIGKILL as forceful termination on Windows.
+ *
+ * @param proc - The subprocess to force-kill
+ */
+export function forceKillProcess(proc: ChildProcess): void {
+  if (proc.killed || proc.exitCode !== null) return;
+  proc.kill("SIGKILL");
+}
+
+/** Registry of active subprocesses for cleanup on teardown. */
+const activeProcesses = new Set<ChildProcess>();
+
+/**
+ * Register a subprocess in the global process registry.
+ * The process is automatically removed from the registry when it exits.
+ *
+ * @param proc - The subprocess to track
+ */
+export function registerProcess(proc: ChildProcess): void {
+  activeProcesses.add(proc);
+  proc.on("exit", () => activeProcesses.delete(proc));
+}
+
+/**
+ * Force-kill all registered subprocesses and clear the registry.
+ * Safe to call multiple times -- no-ops on already-dead processes.
+ */
+export function killAllProcesses(): void {
+  for (const proc of activeProcesses) {
+    forceKillProcess(proc);
+  }
+  activeProcesses.clear();
+}
+
+/**
+ * Force-kill the subprocess after a 500ms grace period.
+ * The Claude CLI hangs after emitting the result message (known bug).
+ * Brief grace period allows final stdout flushing before force-kill.
+ *
+ * @param proc - The Claude subprocess to clean up
+ */
+export function cleanupProcess(proc: ChildProcess): void {
+  setTimeout(() => {
+    forceKillProcess(proc);
+  }, 500);
+}
+
+/**
+ * Attach a data listener to stderr and accumulate output into a buffer.
+ *
+ * @param proc - The Claude subprocess
+ * @returns A function that returns the accumulated stderr string
+ */
+export function captureStderr(proc: ChildProcess): () => string {
+  let buffer = "";
+  proc.stderr!.on("data", (data: Buffer) => {
+    buffer += data.toString();
+  });
+  return () => buffer;
+}
+
+/**
+ * Validate that the Claude CLI is installed and on PATH.
+ * Throws with install instructions if not found.
+ */
+export function validateCliPresence(): void {
+  try {
+    execSync("claude --version", { stdio: "pipe", timeout: 5000 });
+  } catch {
+    throw new Error(
+      "Claude Code CLI not found. Install it: npm install -g @anthropic-ai/claude-code\n" +
+        "Then authenticate: claude auth login",
+    );
+  }
+}
+
+/**
+ * Validate that the Claude CLI is authenticated.
+ * Returns false and warns if not authenticated.
+ *
+ * @returns true if authenticated, false otherwise
+ */
+export function validateCliAuth(): boolean {
+  try {
+    execSync("claude auth status", { stdio: "pipe", timeout: 5000 });
+    return true;
+  } catch {
+    console.warn(
+      "[pi-claude-cli] Claude CLI is not authenticated. " +
+        "Run 'claude auth login' to authenticate.",
+    );
+    return false;
+  }
+}