fix(console): enable conmand remote access + add conman client script

conmand was binding to localhost only (server loopback=on default), so
the conman client on workstations couldn't connect. The intended workflow
is: conman client (workstation) → conmand (pfv-tsys4:7890 over Tailscale)
→ ser2net (TCP 2001-2007) → serial device. Without remote conmand access,
users had to telnet directly to ser2net, which conflicts with conmand's
persistent connections (kickolduser kicks the telnet session immediately).

Changes:
- generate-config.sh: add server loopback=off to conman.conf so conmand
  listens on 0.0.0.0:7890 (reachable via Tailscale)
- query-remote.sh: new script for workstations — installs conman client,
  verifies connectivity, lists or connects to consoles
- README.md: clarify access model (conman primary, telnet emergency only
  with conmand stopped). Document the kickolduser conflict.

💘 Generated with Crush

Assisted-by: Crush:glm-5.2

console/README.md

@@ -64,18 +64,30 @@ All ports listen on the Tailscale IP (`100.70.77.93`).
 
 ### Connect to a console
 
+**Primary method — conman client (with logging + multiplexing):**
+
 ```bash
-# Via conman (with logging + multiplexing):
-conman -f pfv-core-sw01        # attach to console
-conman -q                      # query status of all consoles
-
-# Via telnet (direct, no logging):
-telnet 100.70.77.93 2001       # pfv-core-sw01
-
-# From any Tailscale-connected device:
-telnet pfv-tsys4 2001
+# From any Tailscale-connected workstation:
+conman -d pfv-tsys4:7890 -f pfv-core-sw01     # connect to console
+conman -d pfv-tsys4:7890 -q                    # list all consoles
 ```
 
+Escape sequence: `&.` to disconnect, `&?` for help.
+
+**Direct telnet (emergency only — conflicts with conman):**
+
+```bash
+# Direct telnet to ser2net works ONLY when conmand is stopped, because
+# conmand maintains persistent connections to all 7 TCP ports. Use:
+ssh pfv-tsys4 'systemctl stop conmand'
+telnet pfv-tsys4 2001                          # pfv-core-sw01
+ssh pfv-tsys4 'systemctl start conmand'        # restart when done
+```
+
+**Do NOT use telnet while conmand is running** — conmand will reconnect
+and kick your telnet session immediately ("Connection closed by foreign host").
+The correct workflow is conman client → conmand → ser2net → device.
+
 ### Re-deploy after changing mapping.txt
 
 ```bash