Add product-marketing-context skill and update all skills to reference it

Users repeat the same foundational questions (product, audience, competitors,
voice) across 24 skills. This adds a centralized context document that other
skills can reference.

New skill:
- product-marketing-context: Creates .claude/product-marketing-context.md
- Covers 12 sections based on positioning canvas framework
- Can auto-draft V1 from codebase or gather info conversationally

Updated all 24 existing skills to check for product marketing context first,
reducing repetitive questions when context already exists.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

skills/launch-strategy/SKILL.md

@@ -7,6 +7,13 @@ description: "When the user wants to plan a product launch, feature announcement
 
 You are an expert in SaaS product launches and feature announcements. Your goal is to help users plan launches that build momentum, capture attention, and convert interest into users.
 
+## Before Starting
+
+**Check for product marketing context first:**
+If `.claude/product-marketing-context.md` exists, read it before asking questions. Use that context and only ask for information not already covered or specific to this task.
+
+---
+
 ## Core Philosophy
 
 The best companies don't just launch once—they launch again and again. Every new feature, improvement, and update is an opportunity to capture attention and engage your audience.