feat(tui): open on the token meter, and let the legend name every model

[edwin-zvs]

Follow-ups on the token meter (#1057), all about it being readable when you first meet it.

Default mode is the token meter

A client with no recorded choice now opens on the meter rather than the rain. An absent setting means "never asked" — which covers a fresh install and an upgrade from before the panel had modes at all — and the meter answers a question where the animation is ambience. Anyone who has actually picked a mode keeps it, since that choice is persisted.

Note: the panel itself still defaults to collapsed (matrix_rain_hidden: true, unchanged and long-standing), so on a fresh install this only takes effect once the panel is expanded. Say the word if you want the panel open by default too — that's a separate one-line change with a much bigger first-run footprint.

The legend can name every model

Two limits were cutting it short:

Row cap. The legend was capped at a third of the panel (clamp(h/3, 1, 4)), which is where the "max 4 items" came from — on a 14-row panel that's 4 rows, one entry each. It now takes every row above a three-row graph floor. Three is the least that still reads as a graph rather than a stripe. Naming a series costs one row; not naming it makes its band unreadable, so the trade goes that way until the floor is reached, and only then does the legend truncate.

Palette. 6 series colors → 10, so the collapsed other (N) row is reached far less often. This one can't be removed outright: the palette is the real limit on how many models a legend can name, because listing more names than there are distinguishable colors produces rows nobody can match to a band.

Seven models on a 14-row panel — all named, no +N, no collapse:

 ─⏸ operator ──────────── tokens ⇄ ─ −
             ▂           █   ▁       ▆
     ▆       █▆       ▁  █▃  █       █
    ▁█    █ █▃█  ▅    ▇  ▄▅  ▂ ▂▁    ▆
  ▃ ▇█   ▂▂▁▃▃▃▄█▇▃ ▁▅▁▇█▄█▅▇▅▃█▇ ▄▅██
  ██▃█ ▇▆▁█▂█▃█▁▆▇█▂███▅▂█▅█▄██▄▂ ▁▃▅▅
 ▆▆▃▁█▅▃█▆▄▂▃█▆██▂▃▃▅▅███▁▆▆█▆▅▆▇▆▅▂▅▄
 █▂█▅██▆▄█▅██▇█▄▃██▃█▄▇█▂███▆███████▆█
 ● grok-5 0/s ● muse-spark-1.1 0/s
 ● kimi-k3 0/s ● claude-opus-5 0/s
 ● hermes-4 0/s ● gpt-5.5-codex 0/s
 ● gemini-3-pro 0/s               Σ 0/s

A 7-row panel — graph holds its 3-row floor, legend gets the other 3:

 ─⏸ operator ──────────── tokens ⇄ ─ −
          █             ▄▁▃     ▆
  ▅   ▇   ▂▄ ▄   ▁ ▇▄▄▁▅▁▁▆▆▃▅▃ ▃▂▁  ▄
 ▆▇ ▇▇▆▅▇▁▂█ ▆▃▆▄▇▆▃▃▄▆▅▆▄▇▂▆▅▁ ▅▅█▅▃▆
 ● kimi-k3 0/s ● gemini-3-pro 0/s
 ● gpt-5.5-codex 0/s
 ● claude-opus-5 0/s              Σ 0/s

Bug: a genuine zero reported as <1/s

recent_rate returned an integer, so "computed but produced nothing" and "produced less than a token per second" both arrived as Some(0) and rendered <1/s — claiming output that didn't exist. It's fractional now, and the three states stay distinct: idle (never computed), 0/s (computed, produced nothing), <1/s (produced very little). Both snapshots above show the corrected 0/s.

Test note

matrix_rain_paints_browser_preview_wallpaper counts cells with an Rgb background on the premise that "the rain only ever sets fg" — which the meter's stacked-boundary cells violate. It's testing the rain body specifically, so it now pins the mode explicitly rather than relying on the default.

Specs

• 0019 — records which mode a client with no recorded choice opens on.
• 0167 — graph floor vs. legend rows, the palette as the naming limit, and the three rate states.

Binaries

Touches crates/cli only → the binary is construct.