The file watcher binding (and other node-precompiled .node modules
loaded via dlopen) failed with "libstdc++.so.6: cannot open shared
object file" because systemd services don't inherit the user shell's
LD path. Reuse the nix-ld library list so the service sees the same
common libraries unwrapped binaries get globally.
The opencode-serve unit ran with systemd's minimal default PATH, so
shell commands invoked by the agent (git, make, nix, node, rg, etc.)
were not found. Set systemd.services.opencode-serve.path on both sgx
and amd to a common dev toolset.
Mirror of the sgx opencode setup: systemd service on port 4196 fronted
by nginx with a per-host ACME cert (DNS-01 via internetbs). Adds amd
key + path rule to .sops.yaml so secrets under .secrets/amd/ encrypt
for the host.
