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/growth-scaling.md

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+# Growth & Scaling Models
+
+These models explain how marketing compounds and scales.
+
+## Feedback Loops
+Output becomes input, creating cycles. Positive loops accelerate growth; negative loops create decline.
+
+**Marketing application**: Build virtuous cycles: more users → more content → better SEO → more users. Identify and strengthen positive loops.
+
+## Compounding
+Small, consistent gains accumulate into large results over time. Early gains matter most.
+
+**Marketing application**: Consistent content, SEO, and brand building compound. Start early; benefits accumulate exponentially.
+
+## Network Effects
+A product becomes more valuable as more people use it.
+
+**Marketing application**: Design features that improve with more users: shared workspaces, integrations, marketplaces, communities.
+
+## Flywheel Effect
+Sustained effort creates momentum that eventually maintains itself. Hard to start, easy to maintain.
+
+**Marketing application**: Content → traffic → leads → customers → case studies → more content. Each element powers the next.
+
+## Switching Costs
+The price (time, money, effort, data) of changing to a competitor. High switching costs create retention.
+
+**Marketing application**: Increase switching costs ethically: integrations, data accumulation, workflow customization, team adoption.
+
+## Exploration vs. Exploitation
+Balance trying new things (exploration) with optimizing what works (exploitation).
+
+**Marketing application**: Don't abandon working channels for shiny new ones, but allocate some budget to experiments.
+
+## Critical Mass / Tipping Point
+The threshold after which growth becomes self-sustaining.
+
+**Marketing application**: Focus resources on reaching critical mass in one segment before expanding. Depth before breadth.
+
+## Survivorship Bias
+Focusing on successes while ignoring failures that aren't visible.
+
+**Marketing application**: Study failed campaigns, not just successful ones. The viral hit you're copying had 99 failures you didn't see.