design: three icon candidates, a brief, and the Imagine prompt

The icon cannot carry the product's sentence, so it carries the shortest
true part: something is beating and you can see it.

Three candidates as plain SVG geometry, all rendered through make_icons.py
and judged at 32px rather than at full size. A rows (workload table),
B tab carrying a pulse, C pulse alone. B is the most specific idea and
needs simplifying; A is the clearest and the least distinctive; C wins at
16px but says health monitor, not browser.

Signed-off-by: Christian Sass <csass@binaryranch.com>

docs/design/icon-prompts.md

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+# Vitals icon — brief and Imagine prompt
+
+## What the mark has to say
+
+Vitals is a workload map with browser tab accounting. The icon cannot carry that
+sentence, so it carries the shortest true part: **something is beating, and you
+can see it.**
+
+## Constraints
+
+- 16px is the real test. Everything below that size detail is decoration.
+- Two colors from the Binary Ranch palette: ink `#0a0a0a`, paper `#f0ede8`,
+  accent rust `#d4623a`.
+- No text, no gradients, no shadows.
+- Square, safe inside a rounded-square mask.
+
+## Grok Imagine prompt
+
+> Flat vector app icon, 1:1 square, deep charcoal background `#0a0a0a`. A simple
+> browser tab shape in off-white, drawn as one solid rounded rectangle with a
+> single angled corner at the top right, and a thick rust `#d4623a` heartbeat
+> trace running across its middle: one flat line, one sharp peak up, one sharp
+> trough down, then flat again. Uniform heavy stroke, geometric, no gradients, no
+> shadows, no 3D, no text, no letters, no extra detail. The silhouette must read
+> as a single bold shape at 32 pixels.
+
+Simplification prompt if the result is too busy (image to image):
+
+> Keep the tab shape and remove the corner notch. Keep one peak and one trough
+> only. Make the pulse stroke twice as thick. Two colors, flat, centered, no text.
+
+## Candidates built as geometry
+
+Three hand-drawn SVG candidates live in `docs/design/`, rendered through
+`tools/make_icons.py`:
+
+| file | idea | verdict |
+|---|---|---|
+| `vitals-a-rows.svg` | three workload rows, top one hot | legible, but reads as a generic chart |
+| `vitals-b-tab-pulse.svg` | a browser tab carrying a heartbeat | most on-message, notch dies at 32px |
+| `vitals-c-pulse.svg` | the pulse alone | strongest at 16px, says "health" not "browser" |
+
+Recommended direction: **B, simplified.** Remove the corner notch (it is the
+first casualty at small size), keep one peak and one trough, thicken the stroke.
+That keeps the browser reference that makes the mark specific while surviving the
+tab bar.
+
+Do not ship A. It is the clearest of the three and the least distinctive; it
+could belong to any dashboard.

docs/design/vitals-a-rows.svg

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+<svg xmlns="http://www.w3.org/2000/svg" width="1024" height="1024" viewBox="0 0 1024 1024">
+  <rect x="0" y="0" width="1024" height="1024" rx="232" fill="#0a0a0a"/>
+  <rect x="224" y="300" width="576" height="104" rx="18" fill="#d4623a"/>
+  <rect x="224" y="460" width="432" height="104" rx="18" fill="#f0ede8"/>
+  <rect x="224" y="620" width="288" height="104" rx="18" fill="#f0ede8" opacity="0.55"/>
+</svg>

docs/design/vitals-b-tab-pulse.svg

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+<svg xmlns="http://www.w3.org/2000/svg" width="1024" height="1024" viewBox="0 0 1024 1024">
+  <rect x="0" y="0" width="1024" height="1024" rx="232" fill="#f0ede8"/>
+  <path d="M232 300 h400 l64 72 h128 v352 h-592 z" fill="#0a0a0a"/>
+  <path d="M300 620 h96 l48 -132 l64 232 l64 -176 l40 76 h112"
+        fill="none" stroke="#d4623a" stroke-width="56"
+        stroke-linecap="round" stroke-linejoin="round"/>
+</svg>

docs/design/vitals-c-pulse.svg

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+<svg xmlns="http://www.w3.org/2000/svg" width="1024" height="1024" viewBox="0 0 1024 1024">
+  <rect x="0" y="0" width="1024" height="1024" rx="232" fill="#0a0a0a"/>
+  <path d="M180 700 h180 l60 -150 l90 260 l80 -190 l50 80 h204"
+        fill="none" stroke="#f0ede8" stroke-width="72"
+        stroke-linecap="round" stroke-linejoin="round"/>
+</svg>