Block width was 36 chars (name=20 + gap + rx=7 + gap + tx=7) but the
left sidebar is capped at 34 chars (`_left_sidebar_max_width=34`),
clipping the last 2 chars of the Tx/s column (`Tx/s` → `Tx`, `19.0Kb`
→ `19.0`).
Reduces `_NAME_MAX_WIDTH` from 20 to 18 so the natural row width is
exactly 34, fitting the sidebar without painter-side clipping.
Adds a regression test asserting every rendered row fits in 34 chars.
Replicates v4 ``network.msg_curse()`` default mode (rate display, bits,
two columns):
NETWORK Rx/s Tx/s
eth0 1.1Mb 250.0Kb
wlp0s20f3 43.9Kb 11.7Kb
lo 0b 0b
- Header line ``NETWORK | Rx/s | Tx/s`` with dynamic title color escalation
from any prominent bytes_recv/bytes_sent _level (warning/critical).
- One row per interface; ``is_up=False`` and first-cycle interfaces
(no rate yet) are filtered out (v4 issues #765 + on-the-fly creation).
- Rate values: bytes/s × 8 → bits/s, K/M/G/T scaled, ``b`` suffix; sub-K
values stay raw (e.g. ``0b``) — matches v4 ``auto_unit + 'b'``.
- Long interface names tail-truncated with a leading underscore.
- Per-interface ``_levels`` drive rate cell color + prominent flag.
Hardcoded ``name_max_width=20`` and rate-bits-2col mode for G1. TODO
in the module documents the plumbing needed (max_width + args) to
support --byte / --network-cumul / --network-sum in G2+.
16 new tests in tests/test_plugin_network_render_curses_v5.py.
