By: ananjiani <ananjiani@noreply.codeberg.org>
fix(steammachine): keep the WiFi radio off so it stops competing with Bluetooth (#351)
## Why
The Steam Machine is **wired and has no use for WiFi**, but its radio shares an antenna with the Bluetooth adapter. NetworkManager scans for networks even while disconnected (`wlp6s0` was `DOWN`/`NO-CARRIER` the whole time), and that 2.4 GHz traffic competes with the controller link — which is already fighting a congested band.
Evidence that the radio was live despite being disconnected: it saw **18 access points** at signal 90-95.
## Measured
With a Pro Controller connected, dropping the radio:
```
before after radio off
dropped IMU reports 3.2/min 1.5/min
report gap (delta) 78-105 ms 65-79 ms
avg_delta 15 ms 11 ms
```
Roughly halves the loss, and the report stream gets denser.
## Ceiling — read this before expecting a fix
This does **not** eliminate the problem. The remainder is neighbouring congestion:
```
ch 1 1 AP strongest 70
ch 4 3 APs strongest 82 <- this house's own 2.4 GHz SSIDs
ch 6 3 APs strongest 95
ch 11 3 APs strongest 92
```
`hfcl`/neighbour APs on channels 6 and 11 at signal 92-95 are not ours to change. Eliminating the rest needs physical separation: a USB Bluetooth dongle on an extension cable clear of the chassis and TV.
## Change
Adds a oneshot that runs `rfkill block wifi` after `NetworkManager.service`. It is an `rfkill` block rather than just a NetworkManager disconnect, so the phy cannot be woken by a scan.
## Verification
Confirmed safe on the running host before making it declarative: with the WiFi phy soft-blocked, Bluetooth kept working and improved, and `enp5s0` stayed connected.
Co-authored-by: Ammar <ammar.nanjiani@gmail.com>
Reviewed-on: https://codeberg.org/ananjiani/infra/pulls/351