docs: give the system widgets a shared colour language

Thresholds colour every quantity that has a comfortable range: ok below
the first, warning between, critical above. 25/75 for filesystems, cache
and CPU load; per-sensor pairs for temperatures, because 70C is
unremarkable on a CPU and alarming on an NVMe.

The per-core row becomes an equaliser: sixteen vertical bars rising from
a baseline, coloured by load. Disks become idea2's rings, an icon at the
centre and the arc coloured by usage. Cache highlights its largest
subdirectory.

This needs a `warning` role the dashboard does not currently expose.
udt-palette already resolves it in every scheme, mapping yellow (or
Nord's aurora_yellow) to it globally, and other generators already read
it, so adding it is one word in gen_conky's role tuple plus a
placeholder and a palette line. No scheme file changes.

Three new primitives in lib/card.lua rather than per-widget drawing:
bar, ring, and a threshold helper so all four cards agree on the rule
instead of each re-deriving it.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

1 files changed, 87 insertions, 12 deletions

diff --git a/docs/superpowers/specs/2026-09-17-system-widgets-design.md b/docs/superpowers/specs/2026-09-17-system-widgets-design.md
index eea3a88..9fee4a5 100644
--- a/docs/superpowers/specs/2026-09-17-system-widgets-design.md
+++ b/docs/superpowers/specs/2026-09-17-system-widgets-design.md
@@ -134,22 +134,97 @@ All four follow the fluid convention documented in the README: sizes derive
 from `inner.w` with clamps, the slack is distributed deliberately, and an
 element that cannot fit drops out rather than overlapping.
 
-### A shared bar primitive
+### One colour language across all four cards
 
-`lib/card.lua` gains `card.bar(cr, x, y, w, h, frac, colors, colour)`: a track
-with a filled portion. Three of the four widgets need it (per-core load, RAM,
-filesystem usage), which is the third use that earns the abstraction rather
-than each widget drawing its own rectangles.
+Every quantity that has a comfortable range and an uncomfortable one is
+coloured the same way, so a glance at any card reads without learning a new
+scheme:
 
-It takes an explicit colour so a bar can turn `colors.critical` past a
-threshold, which is what makes a filesystem at 84% readable at a glance.
+| State | Role | Meaning |
+|---|---|---|
+| fine | `ok` | below the first threshold |
+| busy | `warning` | between the thresholds |
+| nearly full / hot | `critical` | above the second |
+
+**`warning` is new to the dashboard palette.** `dashboard.lua`'s `palette()`
+exposes `ok` and `critical` but no middle colour. `udt-palette` already
+resolves `warning` in every scheme: it maps `yellow`, or Nord's
+`aurora_yellow`, to that role globally, the same way it maps `red` to
+`critical` even though `[conky]` never lists it, and other generators already
+read `res['warning']`.
+
+Three places, one line each, none of them a scheme file:
+
+1. `bin/udt-palette` (UDT repo), `gen_conky`: add `"warning"` to the tuple of
+   roles it substitutes. `critical` was added to that same tuple for the error
+   overlay, so this is the established way.
+2. `conky.conf.in`: a `color8 = '@WARNING@'` line.
+3. `dashboard.lua`'s `palette()`: `warning = hex(CFG.color8)`.
+
+Scheme switching keeps working untouched, and every existing scheme gets the
+colour for free.
+
+Thresholds by kind:
+
+- **Filesystems and cache**: 25% and 75%, as requested.
+- **CPU load**: the same 25/75, so a core at rest, a core working and a core
+  pinned are distinguishable at a glance.
+- **Temperatures**: per sensor, because 70C is unremarkable for a CPU and
+  alarming for an NVMe. Each carries its own pair in the widget's binding
+  table, alongside the hwmon path it already needs:
+
+      Tctl        75 / 90
+      Tccd1       75 / 90
+      NVMe        60 / 70
+      Arc pkg     75 / 85
+      Arc VRAM    80 / 90
+      board       60 / 70
+
+  These are starting values, host-specific exactly as the hwmon bindings are,
+  and sit in one table so they are easy to retune once real numbers under load
+  are known.
+
+### Shared primitives in `lib/card.lua`
+
+`card.bar(cr, x, y, w, h, frac, colour)` — a track with a filled portion.
+
+`card.ring(cr, cx, cy, r, frac, colour, colors)` — an open circle with an arc
+covering `frac` of it, after `idea2.png`: the arc starts at twelve o'clock and
+sweeps clockwise, over a dim full-circle track, with room at the centre for a
+glyph.
+
+`card.threshold(frac, warn, crit, colors)` — returns the colour for a value
+against two thresholds. One function so all four widgets agree, and so the
+rule is stated once rather than re-derived per card.
+
+### The per-core row as an equaliser
+
+Sixteen vertical bars across the card, each rising from a common baseline with
+its core's load, coloured by the same thresholds. Reads as a level meter: idle
+cores sit low and green, a compile lights the whole row amber to red.
+
+Bar width and gap derive from the cell. Below the width where sixteen bars
+would each be thinner than about 3px the widget drops to the aggregate bar
+alone rather than drawing an illegible grey smear, which is the same
+drop-rather-than-crush rule the weather arc follows.
+
+### The disks as rings
+
+After `idea2.png`: one ring per filesystem, each with an icon at its centre
+naming what it is (a drive glyph for local, a network glyph for NFS), the arc
+showing usage and coloured by threshold. The mount point and percentage sit
+beside or beneath depending on how many fit across the card width.
+
+Rings wrap to as many rows as the cell allows and, past the point where a ring
+would be too small to read, the widget falls back to the labelled horizontal
+bars `card.bar` already provides.
 
-### The per-core row
+### Cache
 
-Sixteen thin vertical bars across the card width is the one novel layout. Bar
-width derives from the cell, and below the width where sixteen would be thinner
-than about 3px the widget drops to the aggregate bar alone rather than drawing a
-grey smear.
+The total as a heading, then the four largest subdirectories. The largest is
+drawn in `warning` (or `critical` if it dominates, over half the total) while
+the rest stay in `value`, so the thing worth deleting is the thing that catches
+the eye.
 
 ## Staleness and failure