refactor(skills): move marketing-psychology catalogs to references

Keep the decision steps in SKILL.md and move catalogs, examples, and
checklists verbatim to references/ to reduce the context cost of loading the
skill.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

shared/skills/marketing-psychology/references/pricing-psychology.md

@@ -0,0 +1,28 @@
+# Pricing Psychology
+
+These models specifically address how people perceive and respond to prices.
+
+## Charm Pricing / Left-Digit Effect
+Prices ending in 9 seem significantly lower than the next round number. $99 feels much cheaper than $100.
+
+**Marketing application**: Use .99 or .95 endings for value-focused products. The left digit dominates perception.
+
+## Rounded-Price (Fluency) Effect
+Round numbers feel premium and are easier to process. $100 signals quality; $99 signals value.
+
+**Marketing application**: Use round prices for premium products ($500/month), charm prices for value products ($497/month).
+
+## Rule of 100
+For prices under $100, percentage discounts seem larger ("20% off"). For prices over $100, absolute discounts seem larger ("$50 off").
+
+**Marketing application**: $80 product: "20% off" beats "$16 off." $500 product: "$100 off" beats "20% off."
+
+## Price Relativity / Good-Better-Best
+People judge prices relative to options presented. A middle tier seems reasonable between cheap and expensive.
+
+**Marketing application**: Three tiers where the middle is your target. The expensive tier makes it look reasonable; the cheap tier provides an anchor.
+
+## Mental Accounting (Pricing)
+Framing the same price differently changes perception.
+
+**Marketing application**: "$1/day" feels cheaper than "$30/month." "Less than your morning coffee" reframes the expense.