feat: remote tab support — launch agents on remote hosts via SSH

[astetic-dev]

Feature request: remote tab support

Each tab should be able to run either a local or remote agent session.

User flow

1. New tab → choose Local or Remote
2. Remote opens a host picker modal:
   • List of saved hosts with nickname + hostname
   • Live reachability indicator per host (green dot / grey / spinner)
   • + Add host… option at the bottom
3. Selecting a host opens a new tab connected to that machine

Host picker UI

┌──────────────────────────────────────┐
│  Choose a remote machine             │
│                                      │
│  ● Home PC           192.168.1.42   │
│  ● Work Laptop       work.tail…net  │
│  ● Raspberry Pi      pi.local       │
│                                      │
│  ─────────────────────────────────  │
│  + Add host…                        │
└──────────────────────────────────────┘

Add host form fields

• Nickname (display name)
• Hostname / IP
• Port (default 22)
• Username
• SSH key path (file picker)
• Default project path (optional)

"Add & test" button does an immediate reachability check on save.

Data storage

Persist host list as hosts.json in the Tauri app data directory.

{
  "hosts": [
    {
      "id": "uuid",
      "nickname": "Home PC",
      "hostname": "192.168.1.42",
      "port": 22,
      "user": "arjen",
      "key_path": "~/.ssh/id_ed25519",
      "default_project": "/home/arjen/projects/myapp"
    }
  ]
}

Backend (Rust/Tauri)

Required Tauri commands:

• list_hosts() → Vec<Host>
• add_host(host) → Host
• remove_host(id) → ()
• check_reachability(hostname, port) → bool — TCP connect with 2s timeout (no root required)

Reachability checks run in parallel when the modal opens.

SSH execution via russh crate (async, no system SSH dependency):

russh = "0.44"
russh-keys = "0.44"

Network

• Same LAN: direct IP
• Cross-network: Tailscale recommended (stable hostnames, works behind NAT)

Auth

SSH key-based auth (primary). Password auth as optional future addition.