Devices: several headsets, several addresses each, and live connection status

Frame Control can now manage more than one Steam Frame, and reach each at any
of several addresses (LAN IPs per network, its .local name, Tailscale). A
connector in the server tries them all at once, picks the best one that
answers, follows ssh -v through each stage (network, finding, SSH, identity,
login) and streams that to the page. The header shows it live; a new Devices
tab (key 5) manages headsets, addresses and network names.

- ui/frame_devices.py: registry in devices.json, imported from the managed
  ~/.ssh/config blocks; per-headset host key pinning; config block updates.
- ui/frame_network.py: gateway IP+MAC fingerprint, Wi-Fi name, Tailscale.
- ui/frame_link.py: the connector, Test now, Tailscale/mDNS discovery, API.
- server.py: ensure_master delegates to the connector; /api/connection,
  /api/connection/events (SSE), /api/devices.
- Electron: headset switcher and Devices item in the Frame menu.
- frame_connect.py --alias; FRAME_CONTROL_DATA_DIR / FRAME_CONTROL_SSH_DIR
  keep tests off real data.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

tests/fakessh/ssh

@@ -0,0 +1,76 @@
+#!/usr/bin/env python3
+"""A stand-in for OpenSSH's ssh, for tests/test_link.py: prints what `ssh -v` prints at
+each step of a connection, and plays a ControlMaster. What each HostName does comes
+from $FAKESSH_HOSTS (JSON: host -> "ok", "wrong" (a different host key) or "denied");
+every call is appended to $FAKESSH_LOG as a JSON line. POSIX only."""
+import json
+import os
+import signal
+import sys
+import time
+
+args = sys.argv[1:]
+with open(os.environ["FAKESSH_LOG"], "a") as f:
+    f.write(json.dumps(args) + "\n")
+hosts = json.loads(os.environ.get("FAKESSH_HOSTS", "{}"))
+opts = {}
+i = 0
+while i < len(args) and args[i].startswith("-"):
+    if args[i] in ("-o", "-O", "-p", "-l"):
+        key = args[i]
+        val = args[i + 1]
+        if key == "-o":
+            k, _, v = val.partition("=")
+            opts[k.lower()] = v
+        else:
+            opts[key] = val
+        i += 2
+    else:
+        opts[args[i]] = True
+        i += 1
+alias = args[i] if i < len(args) else ""
+host = opts.get("hostname", alias).replace("%%", "%")
+marker = os.path.join(os.environ["FAKESSH_DIR"], "master-" + host.replace("/", "_"))
+say = lambda s: (sys.stderr.write(s + "\n"), sys.stderr.flush())
+
+if "-G" in opts:
+    print(f"hostname {alias}\nport 22\nuser tester")
+    sys.exit(0)
+if opts.get("-O") == "check":
+    sys.exit(0 if os.path.exists(marker) else 255)
+if opts.get("-O") == "exit":
+    if os.path.exists(marker):
+        os.unlink(marker)
+    sys.exit(0)
+
+what = hosts.get(host)
+if what is None:
+    say(f"ssh: Could not resolve hostname {host}: nodename nor servname provided, or not known")
+    sys.exit(255)
+say(f"debug1: Connecting to {host} [127.0.0.1] port {opts.get('port', 22)}.")
+say("debug1: Connection established.")
+say(f"debug1: Authenticating to {host}:22 as '{opts.get('user', 'tester')}'")
+say("debug1: Server host key: ssh-ed25519 SHA256:fakefakefakefakefakefakefakefakefakefakefak")
+if what == "wrong":
+    say("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@")
+    say("@    WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED!     @")
+    say("Host key verification failed.")
+    sys.exit(255)
+say(f"debug1: Host '{opts.get('hostkeyalias', host)}' is known and matches the ED25519 host key.")
+say("debug1: Next authentication method: publickey")
+if what == "denied":
+    say(f"tester@{host}: Permission denied (publickey).")
+    sys.exit(255)
+say(f'Authenticated to {host} ([127.0.0.1]:22) using "publickey".')
+if opts.get("controlmaster") == "yes":
+    open(marker, "w").close()
+    def bye(*_):
+        if os.path.exists(marker):
+            os.unlink(marker)
+        sys.exit(0)
+    signal.signal(signal.SIGTERM, bye)
+    while True:
+        time.sleep(0.2)
+        if not os.path.exists(marker):
+            sys.exit(0)
+sys.exit(0)