Keep the default wpa_supplicant backend (iwd pegged 100% CPU in dense
~100-AP RF and wedged the link), disable NIC power-save + PCIe ASPM to
cut mt7925 scan-deauth frequency, and drop the gateway-ping watchdog
(bornhack drops ICMP to the gateway, so it false-fired and bounced a
working connection every 90s).

Mark wlan links unmanaged by systemd-networkd so NetworkManager is
the sole wifi DHCP client. With networking.useNetworkd enabled, the
auto-generated 40-<iface>.network ran a second DHCP client on the
wifi; the two fought over the lease and routes and dropped the link
every few minutes. Match by Type=wlan so it holds across interface
renames.

nixvim's docs build patches nixos-render-docs with nixpkgs PR#538502,
already merged in our nixpkgs, so the patch fails and breaks the build.
We follow a single nixpkgs, so drop the manpage instead.

nixpkgs default python3 moved to 3.14, but tulir_telethon declares no
3.14 support, breaking evaluation.