actop 1.9.0

Changed

• Net / disk I/O get their own chart sections (N2). The rates shipped in
  1.8.0 as two plain text rows tacked onto the bottom of the Memory box — the
  only telemetry in the dashboard with no history rendering, and mis-filed
  (network throughput is not a memory metric). They now own two sibling
  sections, Network and Disk, each drawing a mirrored pair of charts —
  the inbound trace (↓ In / ↓ Read) grows upward and the outbound one
  (↑ Out / ↑ Write) hangs downward directly beneath it, so the seam where
  they meet reads as a shared zero axis (the btop/vnstat convention) without
  spending a row drawing one. Labels sandwich the pair, so each direction keeps
  its own avg · max at the same box height two separate label+chart stacks
  would cost:
  • The grid preset gains a third paired row (Network | Disk); Power
    keeps its full-width span beneath them. Each section hides itself entirely
    when the platform reports no counters, so Power closes the gap on a
    machine without them.
  • Charts are always auto-scaled — there is no SoC reference throughput for a
    NIC or NVMe controller, so --power-scale profile has no analogue here.
    New L2 helper analytics.io_rate_percent() divides by
    max(floor, rolling_peak x1.25), reusing the multiplier --power-scale auto already uses. Both directions of a box share one denominator, so an
    upload trickle never renders as tall as a saturating download.
  • New floors NET_RATE_FLOOR_BPS (1 MB/s) and DISK_RATE_FLOOR_BPS
    (10 MB/s) stop idle background chatter (mDNS keepalives, APFS journaling)
    from dividing by itself and painting a full-scale chart.
  • Each direction now carries its own avg N · max N context, replacing the
    combined avg ↓N ↑N suffix of the single-row form.
  • BrailleChart gains a fill direction. down anchors the trace at the
    top edge via a second cumulative bit table — exact in dots mode; in
    block mode the downward half quantizes to 2 levels per row, since Block
    Elements ships only ▀ and █ as upper fills and the quarter-blocks at
    U+1FB82/U+1FB85 are missing from many terminal fonts.
  • No alert threshold added: neither bus has a knowable ceiling to saturate
    against, so AlertEngine is untouched. Export output is unchanged — this
    is a presentation-only change.