ssh_exec: accept credentials directly as tool parameters ...

host, username, password, port, key_path are now first-class parameters.
No config file needed — user can pass creds in the chat message.
Ad-hoc connections skip host key verification by default.
Named connections in ssh_hosts.json still work as a shortcut.

Fix SSH password auth: disable key lookup when password is configured ...

asyncssh tried ~/.ssh/* keys before the password, causing PermissionDenied
on hosts that only accept password auth. Now when 'password' is set and no
'client_keys', key auth is disabled entirely.

Filesystem tool: unrestricted mode by default ...

FS_ALLOWED_PATHS=* (default) allows any path, consistent with terminal.
Path check is now lazy (per-request) instead of module-level,
so config is always fresh after restart.
~ expansion added.

Unrestricted terminal mode and SSH tool ...

- Terminal: TERMINAL_ALLOWED_COMMANDS=* (default) runs via shell,
  supports pipes, redirects, subshells; allowlist mode still available
- FS_ALLOWED_PATHS expanded to cover /home /etc /var /opt
- New ssh_exec tool: execute commands on remote hosts via asyncssh,
  supports named connections (ssh_hosts.json) and inline user@host
- ssh_hosts.json gitignored, ssh_hosts.json.example added as reference
- ssh_exec added to server_admin and smart_home profiles

Initial implementation of the agent system core ...

- FastAPI server with REST API and WebSocket streaming
- Modular LLM backend abstraction (Ollama implemented, OpenAI stub)
- Tool system: web_search (ddgs), filesystem, http_request, code_exec, terminal
- Agent profiles: smart_home, server_admin, secretary
- Tool-calling loop with concurrent tool execution
- In-memory session store with SessionStore ABC for future persistence
- Registry pattern for tools, profiles, and backends
- Orchestrator stub as foundation for multi-agent scenarios