feat: FreeBSD and OpenBSD drivers, read side

FreeBSDDriver (`freebsd`) and OpenBSDDriver (`openbsd`) on a shared
BsdDriver, for the BSD VMs netOrk provisions and BSD hosts added by hand
(NetOrk/netork#798).

- SSH over exec channels (napalm-device-types' run_on_transport): no PTY,
  stdout and stderr apart, real exit codes; run_command()/open_stream()
  are public. Root through `sudo -S` with the password on stdin, or
  `sudo -n` without one.
- Facts: hostname, release and running kernel (freebsd-version / uname),
  hardware from SMBIOS (kenv) or hw.* sysctls, uptime from kern.boottime.
- Interfaces and addresses (ifconfig -a: ether/lladdr, hex netmasks,
  scoped IPv6), routes (netstat -rn, OpenBSD's abbreviated networks
  written out, host/broadcast/loopback entries left out), ARP (FreeBSD's
  sentences, OpenBSD's table), users and groups, processes (lstart read as
  one five-word field), cron jobs (system crontab and the login user's).
- Parsers are pure functions, tested on output recorded from FreeBSD 15.1
  (hand-installed and cloud image) and OpenBSD 7.9 (NetOrk/netork#793),
  with internal addresses replaced by documentation ranges.

README.md

@@ -0,0 +1,49 @@
+# napalm-bsd
+
+NAPALM drivers for **FreeBSD** (`freebsd`) and **OpenBSD** (`openbsd`) hosts,
+over SSH, built on [napalm-device-types](https://git.netork.io/NAPALM/napalm-device-types)'
+`OSDriver`. Written for netOrk, which provisions and manages BSD VMs
+(NetOrk/netork#792).
+
+## Design
+
+- One shared `BsdDriver` (`napalm_bsd/base.py`) holds the SSH layer and every
+  reader whose tools agree between the BSDs. `FreeBSDDriver` and
+  `OpenBSDDriver` name only the commands that differ (hostname, release,
+  kernel, hardware, `netstat -rnW` vs `-rn`).
+- Every command runs on its own SSH **exec channel** (`run_on_transport` from
+  napalm-device-types): no PTY to parse a prompt from, stdout and stderr apart,
+  a real exit status. `run_command()` / `open_stream()` are public
+  (`CommandChannelMixin`).
+- Root comes from `sudo -S` with the sudo password on stdin (never on a command
+  line), or `sudo -n` without one, as in napalm-linux. netOrk provisions `sudo`
+  on BSD VMs for that reason; `doas` cannot read a password from stdin.
+- Parsing is in `napalm_bsd/parse.py`, pure functions tested on output recorded
+  from real systems (`tests/fixtures/`, each directory's `COMMANDS.txt` lists
+  what produced it).
+
+## Supported getters
+
+| Getter | FreeBSD | OpenBSD | Source |
+|---|---|---|---|
+| `get_facts` | ✓ | ✓ | `kern.hostname`/`hostname`, `freebsd-version`/`uname`, `kenv smbios.*`/`hw.*`, `kern.boottime` |
+| `get_interfaces`, `get_interfaces_ip` | ✓ | ✓ | `ifconfig -a` |
+| `get_route_to` | ✓ | ✓ | `netstat -rnW` / `netstat -rn` |
+| `get_arp_table` | ✓ | ✓ | `arp -an` |
+| `get_lldp_neighbors` | `{}` | `{}` | no LLDP daemon in either base system |
+| `get_users`, `get_processes`, `get_cron_jobs` | ✓ | ✓ | `/etc/passwd`+`/etc/group`, `ps … lstart`, system crontab + `crontab -l` |
+
+Packages, services, updates (#799) and SNMP (#800) follow.
+
+## Connection arguments
+
+`optional_args`: `port` (22), `key_file`, `sudo_password`, `allow_agent`,
+`look_for_keys` (both off by default).
+
+## Development
+
+```bash
+pip install "napalm-device-types @ git+https://git.netork.io/NAPALM/napalm-device-types.git"
+pip install -e ".[dev]"
+pytest
+```