feat: Multi-session support with tabs, split view, and Mochi integration

- Add SessionContext for central state management
- Add TabBar component for session tabs
- Add SplitLayout for side-by-side session viewing
- Add ChatPanel wrapper component
- Refactor ChatInput to uncontrolled input for performance
- Add SCP file transfer for SSH hosts (Mochi)
- Fix stats undefined crash on session restore
- Store host info in sessions for upload routing

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

backend/server.js

@@ -304,28 +304,60 @@ app.get('/api/browse', async (req, res) => {
 });
 
 // File upload endpoint
-app.post('/api/upload/:sessionId', upload.array('files', 5), (req, res) => {
+app.post('/api/upload/:sessionId', upload.array('files', 5), async (req, res) => {
   try {
     if (!req.files || req.files.length === 0) {
       return res.status(400).json({ error: 'No files uploaded' });
     }
 
-    const uploadedFiles = req.files.map(file => {
+    const sessionId = req.params.sessionId;
+    const session = sessions.get(sessionId);
+    const isSSH = session?.host?.connection?.type === 'ssh';
+
+    const uploadedFiles = [];
+
+    for (const file of req.files) {
       // Convert container path to host path for Claude
       // /projects/.claude-uploads/... -> /home/sumdex/projects/.claude-uploads/...
-      const hostPath = file.path.replace('/projects/', '/home/sumdex/projects/');
-      return {
+      let hostPath = file.path.replace('/projects/', '/home/sumdex/projects/');
+
+      // For SSH hosts, transfer file via SCP
+      if (isSSH && session.host) {
+        const { host: sshHost, user, port = 22 } = session.host.connection;
+        const remotePath = `/tmp/.claude-uploads/${file.filename}`;
+
+        try {
+          // Create remote directory if needed
+          const { execSync } = await import('child_process');
+          execSync(`ssh -o StrictHostKeyChecking=no -p ${port} ${user}@${sshHost} "mkdir -p /tmp/.claude-uploads"`, {
+            timeout: 10000
+          });
+
+          // Transfer file via SCP
+          execSync(`scp -o StrictHostKeyChecking=no -P ${port} "${file.path}" ${user}@${sshHost}:"${remotePath}"`, {
+            timeout: 60000  // 60s for large files
+          });
+
+          hostPath = remotePath;
+          console.log(`[Upload] SCP transferred ${file.filename} to ${session.hostId}:${remotePath}`);
+        } catch (scpErr) {
+          console.error(`[Upload] SCP error for ${file.filename}:`, scpErr.message);
+          // Fall back to local path (won't work but at least doesn't fail)
+        }
+      }
+
+      uploadedFiles.push({
         originalName: file.originalname,
         savedName: file.filename,
-        path: hostPath,  // Use host path so Claude can read it
-        containerPath: file.path,  // Keep container path for reference
+        path: hostPath,
+        containerPath: file.path,
         size: file.size,
         mimeType: file.mimetype,
         isImage: file.mimetype.startsWith('image/')
-      };
-    });
+      });
+    }
 
-    console.log(`[Upload] Session ${req.params.sessionId}: ${uploadedFiles.length} files uploaded`);
+    console.log(`[Upload] Session ${sessionId}: ${uploadedFiles.length} files uploaded`);
     res.json({ files: uploadedFiles });
   } catch (err) {
     console.error('[Upload] Error:', err);
@@ -582,8 +614,11 @@ wss.on('connection', (ws, req) => {
       const { host: sshHost, user, port = 22 } = host.connection;
       const sshTarget = `${user}@${sshHost}`;
 
+      // Use claudePath from config if specified, otherwise default to 'claude'
+      const claudeBin = host.claudePath || 'claude';
+
       // Build the remote command with PATH setup for non-login shells
-      const remoteCmd = `export PATH="$HOME/.local/bin:$PATH" && cd ${projectPath} && claude ${claudeArgs.join(' ')}`;
+      const remoteCmd = `export PATH="$HOME/.local/bin:$PATH" && cd ${projectPath} && ${claudeBin} ${claudeArgs.join(' ')}`;
 
       console.log(`[${sessionId}] SSH to ${sshTarget}:${port} - ${remoteCmd}`);
 
@@ -607,7 +642,7 @@ wss.on('connection', (ws, req) => {
       });
     }
 
-    sessions.set(sessionId, { process: claudeProcess, project: projectPath });
+    sessions.set(sessionId, { process: claudeProcess, project: projectPath, host: host, hostId: hostId });
 
     sendToClient('session_started', {
       sessionId,