Add designlang public-shell pack; tighten auth capture checks

Ran authenticated extract against coulomb.social; session metadata
matched anonymous Bubble defaults, so treat docs/design-extract as a
public shell baseline (PROVENANCE.md). Capture script now refuses to
overwrite storage-state.json with thin anonymous sessions.

docs/design-extract/extras/prompt-pack.md

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+# Prompt pack
+
+Paste-ready prompts for coulomb.social. Use the variant that matches your tool.
+
+## v0.txt
+
+```
+Build a landing page with this exact visual language.
+COLORS:
+  #000000
+  #171717
+  #d08728
+  #ffffff
+  #616161
+  #e5e5e5
+FONTS: [object Object], [object Object], [object Object], [object Object]
+SPACING: 2, 32, 68
+RADIUS: 4, 8
+SHADOWS: rgb(97, 97, 97) 2px 2px 8px 0px
+MATERIAL LANGUAGE: flat
+VOICE: Tone: neutral · Headings: unknown
+SECTIONS (in order):
+- hero
+- features
+- cta
+- footer
+Use Tailwind. Match these tokens exactly. Keep the material language consistent.
+```
+
+## lovable.txt
+
+```
+Clone the design language of this landing page and build a fresh equivalent.
+Visual feel: flat. Tone: neutral · Headings: unknown
+Primary palette: #000000, #171717, #d08728, #ffffff, #616161.
+Typography: [object Object], [object Object], [object Object], [object Object].
+Corner radius vocabulary: 4, 8.
+Shadow vocabulary: rgb(97, 97, 97) 2px 2px 8px 0px.
+Page structure:
+- hero
+- features
+- social proof
+- cta
+- footer
+```
+
+## cursor.md
+
+```
+# Design brief
+Page type: **landing**.
+Material language: **flat**.
+Voice: Tone: neutral · Headings: unknown.
+## Tokens
+```ts
+export const tokens = {
+  colors: ['#000000', '#171717', '#d08728', '#ffffff', '#616161', '#e5e5e5'],
+  fonts: ['[object Object]', '[object Object]', '[object Object]', '[object Object]'],
+  radii: ['4', '8'],
+  shadows: ['rgb(97, 97, 97) 2px 2px 8px 0px'],
+};
+```
+## Sections
+- hero
+- features
+- cta
+- footer
+```
+
+## claude-artifacts.md
+
+```
+Create a React artifact that reproduces this brand's design language.
+Page intent: landing.
+Material language: flat.
+Voice: Tone: neutral · Headings: unknown.
+Colors to use: #000000, #171717, #d08728, #ffffff, #616161, #e5e5e5.
+Fonts: [object Object], [object Object], [object Object], [object Object].
+Radius vocabulary: 4, 8.
+Sections:
+- hero
+- features
+- cta
+- footer
+Use Tailwind via CDN, lucide-react for icons, and keep the material language consistent across sections. Do not add extra decorative elements outside this vocabulary.
+```
+
+## Recipes
+
+### button
+
+# Recipe: button
+Build one button component that matches this brand.
+Palette: #000000, #171717, #d08728, #ffffff, #616161, #e5e5e5
+Typography: [object Object], [object Object], [object Object], [object Object]
+Material: flat
+Signals: Radius: 4, 8 · Shadows: rgb(97, 97, 97) 2px 2px 8px 0px
+## Anatomy (detected)
+```json
+{
+  "kind": "button",
+  "structuralHash": "button>svg",
+  "instanceCount": 1,
+  "variants": [
+    {
+      "css": {
+        "background": "rgba(0, 0, 0, 0)",
+        "color": "rgb(208, 135, 40)",
+        "padding": "5px 5px 5px 5px",
+        "borderRadius": "4px",
+        "border": "0px none rgb(208, 135, 40)",
+        "fontSize": "13.3333px",
+        "fontWeight": "400"
+      },
+      "instanceCount": 1
+    }
+  ]
+}
+```
+

docs/design-extract/extras/voice.json

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+{
+  "tone": "neutral",
+  "pronoun": "third-person",
+  "headingStyle": "unknown",
+  "headingLengthClass": "tight",
+  "ctaVerbs": [],
+  "buttonPatterns": [],
+  "sampleHeadings": [],
+  "stats": {
+    "buttons": 0,
+    "headings": 0
+  }
+}