fix(pi): add snap node compatibility diagnostics and documentation

- Added detailed error logging to detect snap node compatibility issues
- When Pi process exits with code 1, log helpful diagnostic info including node path
- Add hint to check for snap node and reinstall via apt/nvm
- Create SNAP_NODE_COMPATIBILITY.md with full troubleshooting guide
- Document root cause: snap node has file descriptor incompatibility with Bun.spawn stdin pipes
- Provide clear installation instructions for NodeSource and nvm alternatives

src/servers/api/auth/verify.ts

@@ -6,6 +6,7 @@ import argon2 from 'argon2';
 import * as errors from '@@/custom-errors';
 import { validatePassword } from './validate-password';
 import { validateUsername } from './validate-username';
+import { provisionLinuxUser } from '../users/provision';
 
 export const verifyHandler: Handler = async function (ctx) {
   const { verificationCode, name, username, password, confirmPassword } = ctx.get('body');
@@ -42,6 +43,11 @@ export const verifyHandler: Handler = async function (ctx) {
   const finalUser = await getUserById(userInfo.id);
   if (!finalUser) throw errors.NOT_FOUND('User not found');
 
+  // Provision Linux user for terminal/Pi/Claude Code isolation
+  provisionLinuxUser(finalUser.email, finalUser.username ?? '').catch((err) => {
+    console.error('[verify] failed to provision Linux user:', err);
+  });
+
   // Issue a token so the user is logged in immediately
   const token = await sign({
     id: finalUser.id,