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/buyer-psychology.md

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+# Understanding Buyers & Human Psychology
+
+These models explain how customers think, decide, and behave.
+
+## Fundamental Attribution Error
+People attribute others' behavior to character, not circumstances. "They didn't buy because they're not serious" vs. "The checkout was confusing."
+
+**Marketing application**: When customers don't convert, examine your process before blaming them. The problem is usually situational, not personal.
+
+## Mere Exposure Effect
+People prefer things they've seen before. Familiarity breeds liking.
+
+**Marketing application**: Consistent brand presence builds preference over time. Repetition across channels creates comfort and trust.
+
+## Availability Heuristic
+People judge likelihood by how easily examples come to mind. Recent or vivid events seem more common.
+
+**Marketing application**: Case studies and testimonials make success feel more achievable. Make positive outcomes easy to imagine.
+
+## Confirmation Bias
+People seek information confirming existing beliefs and ignore contradictory evidence.
+
+**Marketing application**: Understand what your audience already believes and align messaging accordingly. Fighting beliefs head-on rarely works.
+
+## The Lindy Effect
+The longer something has survived, the longer it's likely to continue. Old ideas often outlast new ones.
+
+**Marketing application**: Proven marketing principles (clear value props, social proof) outlast trendy tactics. Don't abandon fundamentals for fads.
+
+## Mimetic Desire
+People want things because others want them. Desire is socially contagious.
+
+**Marketing application**: Show that desirable people want your product. Waitlists, exclusivity, and social proof trigger mimetic desire.
+
+## Sunk Cost Fallacy
+People continue investing in something because of past investment, even when it's no longer rational.
+
+**Marketing application**: Know when to kill underperforming campaigns. Past spend shouldn't justify future spend if results aren't there.
+
+## Endowment Effect
+People value things more once they own them.
+
+**Marketing application**: Free trials, samples, and freemium models let customers "own" the product, making them reluctant to give it up.
+
+## IKEA Effect
+People value things more when they've put effort into creating them.
+
+**Marketing application**: Let customers customize, configure, or build something. Their investment increases perceived value and commitment.
+
+## Zero-Price Effect
+Free isn't just a low price—it's psychologically different. "Free" triggers irrational preference.
+
+**Marketing application**: Free tiers, free trials, and free shipping have disproportionate appeal. The jump from $1 to $0 is bigger than $2 to $1.
+
+## Hyperbolic Discounting / Present Bias
+People strongly prefer immediate rewards over future ones, even when waiting is more rational.
+
+**Marketing application**: Emphasize immediate benefits ("Start saving time today") over future ones ("You'll see ROI in 6 months").
+
+## Status-Quo Bias
+People prefer the current state of affairs. Change requires effort and feels risky.
+
+**Marketing application**: Reduce friction to switch. Make the transition feel safe and easy. "Import your data in one click."
+
+## Default Effect
+People tend to accept pre-selected options. Defaults are powerful.
+
+**Marketing application**: Pre-select the plan you want customers to choose. Opt-out beats opt-in for subscriptions (ethically applied).
+
+## Paradox of Choice
+Too many options overwhelm and paralyze. Fewer choices often lead to more decisions.
+
+**Marketing application**: Limit options. Three pricing tiers beat seven. Recommend a single "best for most" option.
+
+## Goal-Gradient Effect
+People accelerate effort as they approach a goal. Progress visualization motivates action.
+
+**Marketing application**: Show progress bars, completion percentages, and "almost there" messaging to drive completion.
+
+## Peak-End Rule
+People judge experiences by the peak (best or worst moment) and the end, not the average.
+
+**Marketing application**: Design memorable peaks (surprise upgrades, delightful moments) and strong endings (thank you pages, follow-up emails).
+
+## Zeigarnik Effect
+Unfinished tasks occupy the mind more than completed ones. Open loops create tension.
+
+**Marketing application**: "You're 80% done" creates pull to finish. Incomplete profiles, abandoned carts, and cliffhangers leverage this.
+
+## Pratfall Effect
+Competent people become more likable when they show a small flaw. Perfection is less relatable.
+
+**Marketing application**: Admitting a weakness ("We're not the cheapest, but...") can increase trust and differentiation.
+
+## Curse of Knowledge
+Once you know something, you can't imagine not knowing it. Experts struggle to explain simply.
+
+**Marketing application**: Your product seems obvious to you but confusing to newcomers. Test copy with people unfamiliar with your space.
+
+## Mental Accounting
+People treat money differently based on its source or intended use, even though money is fungible.
+
+**Marketing application**: Frame costs in favorable mental accounts. "$3/day" feels different than "$90/month" even though it's the same.
+
+## Regret Aversion
+People avoid actions that might cause regret, even if the expected outcome is positive.
+
+**Marketing application**: Address regret directly. Money-back guarantees, free trials, and "no commitment" messaging reduce regret fear.
+
+## Bandwagon Effect / Social Proof
+People follow what others are doing. Popularity signals quality and safety.
+
+**Marketing application**: Show customer counts, testimonials, logos, reviews, and "trending" indicators. Numbers create confidence.