feat: implement HTTP polling to bypass WebSocket issue

The WebSocket closes immediately with code 1006 due to nginx/proxy
issues. This implementation completely bypasses WebSocket for
terminal output by using HTTP polling instead.

Architecture:
- Server buffers PTY output in memory (outputBuffer array)
- Frontend polls every 100ms via GET /terminals/:id/output?since=N
- Output entries have monotonically increasing index
- Old output is automatically cleaned up after 5 minutes
- Commands sent via HTTP POST (already implemented)

Changes:
- terminal-service.js: Added bufferOutput(), getTerminalOutput()
- terminal.js: Added startPolling(), stopPolling(), sendTerminalResize()
- server.js: Added GET /terminals/:id/output and POST /terminals/:id/resize
- No WebSocket needed for output display (keeps legacy compatibility)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

server.js

@@ -1528,6 +1528,46 @@ app.post('/claude/api/terminals/:id/input', requireAuth, (req, res) => {
     res.status(500).json({ error: 'Failed to send input' });
   }
 });
+
+// Get terminal output via HTTP polling (bypasses WebSocket issue)
+app.get('/claude/api/terminals/:id/output', requireAuth, (req, res) => {
+  try {
+    const sinceIndex = parseInt(req.query.since) || 0;
+    const result = terminalService.getTerminalOutput(req.params.id, sinceIndex);
+
+    if (result.success) {
+      res.json(result);
+    } else {
+      res.status(404).json({ error: result.error });
+    }
+  } catch (error) {
+    console.error('Error getting terminal output:', error);
+    res.status(500).json({ error: 'Failed to get output' });
+  }
+});
+
+// Resize terminal via HTTP
+app.post('/claude/api/terminals/:id/resize', requireAuth, (req, res) => {
+  try {
+    const { cols, rows } = req.body;
+
+    if (!cols || !rows) {
+      res.status(400).json({ error: 'Missing cols or rows parameter' });
+      return;
+    }
+
+    const result = terminalService.resizeTerminal(req.params.id, cols, rows);
+
+    if (result.success) {
+      res.json({ success: true });
+    } else {
+      res.status(404).json({ error: result.error });
+    }
+  } catch (error) {
+    console.error('Error resizing terminal:', error);
+    res.status(500).json({ error: 'Failed to resize terminal' });
+  }
+});
 
 // Get recent directories for terminal picker
 app.get('/claude/api/files/recent-dirs', requireAuth, (req, res) => {