fix(webui): colour each DISK I/O column by the direction it prints

[ntdatt812]

In the WebUI's DISK I/O table the read and write columns wear each other's alert.

disks() builds each row's values like this (plugin-diskio.vue:79-86):

bitrate: {
  txps: bytes(diskioData["read_bytes_rate_per_sec"]),
  rxps: bytes(diskioData["write_bytes_rate_per_sec"]),
},

txps holds the read rate and rxps the write rate — the keys read the other way round, which is the whole trap. The cells then did:

column	prints	decoration it asked for
Rps	bitrate.txps (read)	write_bytes_rate_per_sec
Wps	bitrate.rxps (write)	read_bytes_rate_per_sec
ms/opR	latency.txps (read)	write_latency
ms/opW	latency.rxps (write)	read_latency

update_views() computes the two directions separately — get_alert(..., header='rx') and header='tx' for the bitrates, rx_latency/tx_latency for the latencies — so these are four distinct values, not one shared style. A disk saturated by reads therefore left the read column plain and lit up the write column instead.

The curses UI is not affected: msg_curse pairs each printed value with its own field (read_bytes with the read rate, write_bytes with the write rate), so the two interfaces disagreed.

The change swaps the four getDecoration field names so each cell asks for the field it prints, and names the txps/rxps trap in the one place those keys are assigned, since that naming is what makes the mistake easy to repeat.

Verification

npx eslint js/components/plugin-diskio.vue reports the same 5 warnings before and after the change (4 × vue/first-attribute-linebreak, 1 × vue/require-default-prop, all pre-existing) and 0 errors. There is no test runner under glances/outputs/static — only lint — so there is nothing to add a unit test to; the argument is the field mapping above, which is checkable by reading disks() next to the four cells.