fix(coding-agent): work around Bun empty process.env inside sandbox (#3807)

Bun bug oven-sh/bun#27802 causes process.env to be empty when running inside a Linux sandbox (Landlock/seccomp).
This breaks npm resolution because PATH is missing, crashing pi on startup with:

  Failed to run npm root -g: Executable not found in $PATH: "npm"

Add getSandboxEnv() to read /proc/self/environ as a fallback on Linux when process.env has zero keys.
Pass this env to all spawn calls in package-manager.ts.
Also fix runCommandSync error handling: check result.error in addition to result.status, and include result.error?.message in the error text so spawn failures (e.g. ENOENT) produce useful diagnostics instead of "null".

Fixes #3806

packages/coding-agent/src/core/package-manager.ts

@@ -2,6 +2,26 @@ import { type ChildProcess, type ChildProcessByStdio, spawn, spawnSync } from "n
 import { createHash } from "node:crypto";
 import { existsSync, mkdirSync, readdirSync, readFileSync, rmSync, statSync, writeFileSync } from "node:fs";
 import { homedir, tmpdir } from "node:os";
+
+function getEnv(): NodeJS.ProcessEnv {
+	if (process.platform !== "linux" || Object.keys(process.env).length > 0) {
+		return process.env;
+	}
+	try {
+		const data = readFileSync("/proc/self/environ", "utf-8");
+		const env: NodeJS.ProcessEnv = {};
+		for (const entry of data.split("\0")) {
+			const idx = entry.indexOf("=");
+			if (idx > 0) {
+				env[entry.slice(0, idx)] = entry.slice(idx + 1);
+			}
+		}
+		return env;
+	} catch {
+		return process.env;
+	}
+}
+
 import { basename, dirname, join, relative, resolve, sep } from "node:path";
 import type { Readable } from "node:stream";
 import { globSync } from "glob";
@@ -2326,6 +2346,7 @@ export class DefaultPackageManager implements PackageManager {
 			cwd: options?.cwd,
 			stdio: isStdoutTakenOver() ? ["ignore", 2, 2] : "inherit",
 			shell: this.shouldUseWindowsShell(command),
+			env: getEnv(),
 		});
 	}
 
@@ -2334,11 +2355,12 @@ export class DefaultPackageManager implements PackageManager {
 		args: string[],
 		options?: { cwd?: string; env?: Record<string, string> },
 	): ChildProcessByStdio<null, Readable, Readable> {
+		const baseEnv = getEnv();
 		return spawn(command, args, {
 			cwd: options?.cwd,
 			stdio: ["ignore", "pipe", "pipe"],
 			shell: this.shouldUseWindowsShell(command),
-			env: options?.env ? { ...process.env, ...options.env } : process.env,
+			env: options?.env ? { ...baseEnv, ...options.env } : baseEnv,
 		});
 	}
 
@@ -2405,9 +2427,12 @@ export class DefaultPackageManager implements PackageManager {
 			stdio: ["ignore", "pipe", "pipe"],
 			encoding: "utf-8",
 			shell: this.shouldUseWindowsShell(command),
+			env: getEnv(),
 		});
-		if (result.status !== 0) {
-			throw new Error(`Failed to run ${command} ${args.join(" ")}: ${result.stderr || result.stdout}`);
+		if (result.error || result.status !== 0) {
+			throw new Error(
+				`Failed to run ${command} ${args.join(" ")}: ${result.error?.message || result.stderr || result.stdout}`,
+			);
 		}
 		return (result.stdout || result.stderr || "").trim();
 	}