feat: add SSH remote workspace support

[bobleer]

Summary

• SSH connection management — saved connections with private key, SSH agent, and password authentication; connection tested before save
• Remote file system via SFTP — read, write, edit, delete, rename; all agentic tools (file read/write/edit, bash, glob, grep) routed through SSH when the active workspace is remote
• Remote terminal sessions — full PTY over SSH, integrated into the existing terminal panel
• Multi-workspace registry — replaced single global RemoteWorkspaceState with a path-keyed HashMap, allowing multiple concurrent remote workspaces without path conflicts
• Per-workspace connection status indicator — colored dot (green/amber/red) next to the hostname in the sidebar; pulses while reconnecting
• Auto-reconnect on startup — retries up to 5 times with 10 s intervals; workspace stays visible in the sidebar with an error state if all retries fail
• Session list timing fix — flowChatStore.initializeFromDisk() is re-invoked after SSH reconnect completes, fixing a race where the session list loaded before the workspace was registered in the state manager
• Snapshot/rollback graceful no-op for remote workspaces — rollback commands return an empty success instead of "Workspace directory does not exist"; snapshot recording in the agentic tool pipeline is bypassed for remote paths

Test plan

• Connect to a remote server via SSH (key auth and agent auth)
• Open a remote directory; verify file tree loads correctly
• Edit/create/delete files via the agent; verify changes appear on the remote server
• Open a remote terminal and run commands
• Open two remote workspaces simultaneously; verify each shows correct file tree
• Restart the app; verify both remote workspaces restore with correct status dots
• Verify that rollback does not error on a remote workspace session
• Verify that local workspaces are unaffected by all of the above

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