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/persuasion.md

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+# Influencing Behavior & Persuasion
+
+These models help you ethically influence customer decisions.
+
+## Reciprocity Principle
+People feel obligated to return favors. Give first, and people want to give back.
+
+**Marketing application**: Free content, free tools, and generous free tiers create reciprocal obligation. Give value before asking for anything.
+
+## Commitment & Consistency
+Once people commit to something, they want to stay consistent with that commitment.
+
+**Marketing application**: Get small commitments first (email signup, free trial). People who've taken one step are more likely to take the next.
+
+## Authority Bias
+People defer to experts and authority figures. Credentials and expertise create trust.
+
+**Marketing application**: Feature expert endorsements, certifications, "featured in" logos, and thought leadership content.
+
+## Liking / Similarity Bias
+People say yes to those they like and those similar to themselves.
+
+**Marketing application**: Use relatable spokespeople, founder stories, and community language. "Built by marketers for marketers" signals similarity.
+
+## Unity Principle
+Shared identity drives influence. "One of us" is powerful.
+
+**Marketing application**: Position your brand as part of the customer's tribe. Use insider language and shared values.
+
+## Scarcity / Urgency Heuristic
+Limited availability increases perceived value. Scarcity signals desirability.
+
+**Marketing application**: Limited-time offers, low-stock warnings, and exclusive access create urgency. Only use when genuine.
+
+## Foot-in-the-Door Technique
+Start with a small request, then escalate. Compliance with small requests leads to compliance with larger ones.
+
+**Marketing application**: Free trial → paid plan → annual plan → enterprise. Each step builds on the last.
+
+## Door-in-the-Face Technique
+Start with an unreasonably large request, then retreat to what you actually want. The contrast makes the second request seem reasonable.
+
+**Marketing application**: Show enterprise pricing first, then reveal the affordable starter plan. The contrast makes it feel like a deal.
+
+## Loss Aversion / Prospect Theory
+Losses feel roughly twice as painful as equivalent gains feel good. People will work harder to avoid losing than to gain.
+
+**Marketing application**: Frame in terms of what they'll lose by not acting. "Don't miss out" beats "You could gain."
+
+## Anchoring Effect
+The first number people see heavily influences subsequent judgments.
+
+**Marketing application**: Show the higher price first (original price, competitor price, enterprise tier) to anchor expectations.
+
+## Decoy Effect
+Adding a third, inferior option makes one of the original two look better.
+
+**Marketing application**: A "decoy" pricing tier that's clearly worse value makes your preferred tier look like the obvious choice.
+
+## Framing Effect
+How something is presented changes how it's perceived. Same facts, different frames.
+
+**Marketing application**: "90% success rate" vs. "10% failure rate" are identical but feel different. Frame positively.
+
+## Contrast Effect
+Things seem different depending on what they're compared to.
+
+**Marketing application**: Show the "before" state clearly. The contrast with your "after" makes improvements vivid.