Add per-process network drawer to the Network widget

Clicking the Network pill now toggles a drawer listing processes ranked
by network throughput, refreshed live only while open — mirroring the
CPU widget's top-processes drawer.

services/topnet.sh (single-shot, like topproc.sh) takes two `ss` snapshots
procInterval apart, diffs each TCP socket's cumulative rx/tx bytes by inode,
sums positive deltas per owning PID, and prints ranked "N <rx/s> <tx/s>
<name>" frames. SysStats re-runs it while netProcPollEnabled (drawer open)
using the same SplitParser-accumulate / parse-on-exit / re-arm plumbing as
procScan. Network.qml wraps its Pill in an Item and hangs a fixed-size
PopupWindow drawer off it.

ss (iproute2) is added to runtimeInputs since per-process byte accounting
has no virtual-file equivalent. Caveat: ss only exposes byte counters for
TCP sockets, so UDP/QUIC traffic is not attributed.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

flake.nix

@@ -24,12 +24,14 @@
           qsPkg = quickshell.packages.${pkgs.system}.default;
 
           # Runtime tools the bar relies on: discover.sh (one-shot hardware
-          # probe) and the periodic `df` for disk usage. Everything else is
-          # read from /proc and /sys directly in QML.
+          # probe), the periodic `df` for disk usage, and `ss` (iproute2) for
+          # the per-process network drawer (topnet.sh). Everything else is read
+          # from /proc and /sys directly in QML.
           runtimeInputs = [
             qsPkg
             pkgs.bash
             pkgs.coreutils # df, cat
+            pkgs.iproute2  # ss, for topnet.sh per-process network usage
           ];
 
           # Self-contained font set so Nerd Font glyphs always render,
@@ -69,6 +71,7 @@
             quickshell.packages.${pkgs.system}.default
             pkgs.bash
             pkgs.coreutils
+            pkgs.iproute2 # ss, for topnet.sh
             pkgs.nerd-fonts.jetbrains-mono
             pkgs.inter
             pkgs.qt6.qtdeclarative # qmlls / qmlformat for editing