Repaint to jet-black + atomic-tangerine skin, add consultant-special 2×2

Why: the default skin was too warm/neutral and the pyramid + venn never
quite read the way they should. Also prepping for public sharing, so the
example diagrams needed to drop the littlemight-specific copy.

Changes:
- New five-color palette: jet-black ink, atomic-tangerine accent,
  white-smoke paper, blue-slate muted, silver hairlines. Replaces
  warm-stone + rust across every variant + dark-mode tokens.
- Default background is clean paper; dot grid + framed container are
  now opt-in variants (uncomment in template to enable).
- New consultant-special quadrant variant (example-quadrant-consultant.html)
  — 2×2 scenario matrix with named cells, double-ended axes, one focal
  quadrant; house skin, not a separate visual language.
- Pyramid redrawn as a true triangular silhouette with shared edges on
  one slope (stacked polygons on a single triangle outline, no kinks).
- Venn redesigned: dark-fill triple-intersection with white text,
  circle labels moved inside non-overlap lobes, pair-overlap labels
  removed, legend dropped.
- Example content genericized (content site / product timeline /
  content platform instead of littlemight-branded copy).
- Screenshots regenerated at 2× DPI; added quadrant-consultant.png
  (14th diagram in the gallery).
- README: hero-first opener, preserved Why-I-built-it section, UTM
  tags on littlemight + bestself links, palette description updated.

references/type-sequence.md

@@ -20,13 +20,13 @@
 ## Lifeline primitive
 ```svg
 <line x1="CX" y1="TOP" x2="CX" y2="BOTTOM"
-      stroke="rgba(11,13,11,0.20)" stroke-width="1" stroke-dasharray="3,3"/>
+      stroke="rgba(45,49,66,0.20)" stroke-width="1" stroke-dasharray="3,3"/>
 ```
 
 ## Activation bar primitive
 ```svg
 <rect x="CX-4" y="TOP" width="8" height="H"
-      fill="rgba(11,13,11,0.06)" stroke="#52534e" stroke-width="0.8"/>
+      fill="rgba(45,49,66,0.06)" stroke="#4f5d75" stroke-width="0.8"/>
 ```
 
 ## Examples