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/terminal/pty-sidecar.mjs

@@ -1,3 +1,6 @@
+// Ignore SIGINT — sudo/pty child processes may propagate it
+process.on('SIGINT', () => {});
+
 import http from 'node:http';
 import { existsSync } from 'node:fs';
 import { cp, mkdir } from 'node:fs/promises';
@@ -14,10 +17,8 @@ const run = (cmd, args, opts = {}) =>
   });
 
 const __dirname = dirname(fileURLToPath(import.meta.url));
-const isDocker = existsSync('/opt/terminal-templates/.zshrc');
 
-const templateDir = isDocker ? '/opt/terminal-templates' : join(__dirname, 'templates');
-const ohMyZshSource = isDocker ? '/opt/oh-my-zsh' : null;
+const templateDir = join(__dirname, 'templates');
 
 const port = Number(process.env.TERMINAL_PTY_PORT ?? '5337');
 const host = process.env.TERMINAL_PTY_HOST ?? '127.0.0.1';
@@ -64,18 +65,7 @@ const ensureUserFiles = async (homeDir) => {
 
   const ohMyZshPath = join(homeDir, '.oh-my-zsh');
   if (!existsSync(ohMyZshPath)) {
-    if (ohMyZshSource && existsSync(ohMyZshSource)) {
-      await cp(ohMyZshSource, ohMyZshPath, { recursive: true });
-    } else {
-      await run('git', ['clone', '--depth=1', 'https://github.com/ohmyzsh/ohmyzsh.git', ohMyZshPath]);
-    }
-  }
-
-  if (!isDocker) {
-    const starshipBin = join(homeDir, '.local', 'bin', 'starship');
-    if (!existsSync(starshipBin)) {
-      await run('sh', ['-c', 'curl -sS https://starship.rs/install.sh | sh -s -- -y -b "$HOME/.local/bin"'], { env: { ...process.env, HOME: homeDir } });
-    }
+    await run('git', ['clone', '--depth=1', 'https://github.com/ohmyzsh/ohmyzsh.git', ohMyZshPath]);
   }
 };
 
@@ -145,16 +135,31 @@ wss.on('connection', (ws) => {
       const cwd = msg.cwd ?? process.cwd();
       const homeDir = msg.homeDir ?? process.cwd();
       const userLabel = msg.userLabel ?? 'officer';
+      const username = msg.username ?? null;
       const cols = msg.cols ?? 80;
       const rows = msg.rows ?? 24;
       const isHost = !!msg.host;
 
+      let spawnCommand;
+      let spawnArgs;
       let ptyEnv;
+
       if (isHost) {
+        // Host session — spawn shell directly as current user
+        spawnCommand = shell.command;
+        spawnArgs = shell.args ?? [];
         ptyEnv = { ...process.env, TERM: 'xterm-256color', ...(msg.env ?? {}) };
+      } else if (username) {
+        // User session — spawn via sudo -u as the target Linux user
+        spawnCommand = 'sudo';
+        spawnArgs = ['-u', username, '-i', '/bin/zsh'];
+        ptyEnv = {
+          TERM: 'xterm-256color',
+        };
       } else {
-        const prompt = `${userLabel} in %~ %# `;
-        const bashPrompt = `${userLabel} \\w \\$ `;
+        // Fallback — direct spawn with custom env (legacy)
+        spawnCommand = shell.command;
+        spawnArgs = shell.args ?? [];
 
         try {
           await ensureUserFiles(homeDir);
@@ -171,19 +176,21 @@ wss.on('connection', (ws) => {
           USER: userLabel,
           LOGNAME: userLabel,
           OFFICER_TERMINAL_USER: userLabel,
-          PROMPT: prompt,
-          PS1: bashPrompt,
           TERM: 'xterm-256color',
         };
       }
 
+      // For username sessions, don't set cwd — sudo -u -i will cd to the user's home.
+      // node-pty does chdir before exec, so it would fail if the service user can't access the dir.
+      const ptyCwd = username ? undefined : cwd;
+
       let term;
       try {
-        term = pty.spawn(shell.command, shell.args ?? [], {
+        term = pty.spawn(spawnCommand, spawnArgs, {
           name: 'xterm-256color',
           cols,
           rows,
-          cwd,
+          cwd: ptyCwd,
           env: ptyEnv,
         });
       } catch (err) {