v1.2.1/#22: LMCP_HOST + LMCP_CONF env support

Adds two env vars to the packaged server.lua so hosts can switch
fully to the packaged entrypoint (combined with v1.2.0's tools.d/
plugin scan):

  LMCP_HOST — interface to bind on (default 0.0.0.0). Hosts that
              need .18-only binding (hertz) or similar single-NIC
              constraints set this. Threaded into lmcp.new opts.host.
  LMCP_CONF — path to a conf file with bearer-token entries (e.g.
              /opt/herding/etc/hertz-tools.conf). Read by lmcp.lua's
              read_conf; the `.godparticle` entry becomes the bearer
              token. Threaded into lmcp.new opts.conf.

Both unset → unchanged behavior (binds 0.0.0.0, no conf file).

Together with v1.2.0's tools.d/ scan, this lets a host like hertz
ship NO override server.lua — just an /opt/lmcp/tools.d/hertz.lua
plugin file and a systemd unit that points at the packaged
server.lua with LMCP_HOST=192.168.88.18 + LMCP_CONF=/opt/herding/
etc/hertz-tools.conf. apt upgrade then delivers all packaged
improvements automatically.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

server.lua

@@ -200,6 +200,13 @@ end
 local server_name = os.getenv("LMCP_NAME") or (WINDOWS and "windows-tools" or "linux-tools")
 local server = lmcp.new(server_name, {
     port = tonumber(os.getenv("LMCP_PORT") or arg[1]) or 8080,
+    -- LMCP_HOST: bind interface (default 0.0.0.0). Hosts that need
+    -- single-interface binding (hertz: 192.168.88.18 only) set this.
+    host = os.getenv("LMCP_HOST"),
+    -- LMCP_CONF: path to a conf file with bearer-token entries
+    -- (e.g. /opt/herding/etc/hertz-tools.conf). Read by lmcp.lua's
+    -- read_conf; the `.godparticle` entry becomes the bearer token.
+    conf = os.getenv("LMCP_CONF"),
 })
 
 -- ---- Tools ----