docs: add PR thinking path guidance to contributing

CONTRIBUTING.md

@@ -7,6 +7,7 @@ We really appreciate both small fixes and thoughtful larger changes.
 ## Two Paths to Get Your Pull Request Accepted
 
 ### Path 1: Small, Focused Changes (Fastest way to get merged)
+
 - Pick **one** clear thing to fix/improve
 - Touch the **smallest possible number of files**
 - Make sure the change is very targeted and easy to review
@@ -16,6 +17,7 @@ We really appreciate both small fixes and thoughtful larger changes.
 These almost always get merged quickly when they're clean.
 
 ### Path 2: Bigger or Impactful Changes
+
 - **First** talk about it in Discord → #dev channel  
   → Describe what you're trying to solve  
   → Share rough ideas / approach
@@ -30,12 +32,43 @@ These almost always get merged quickly when they're clean.
 PRs that follow this path are **much** more likely to be accepted, even when they're large.
 
 ## General Rules (both paths)
+
 - Write clear commit messages
 - Keep PR title + description meaningful
 - One PR = one logical change (unless it's a small related group)
 - Run tests locally first
 - Be kind in discussions 😄
 
+## Writing a Good PR message
+
+Please include a "thinking path" at the top of your PR message that explains from the top of the project down to what you fixed. E.g.:
+
+### Thinking Path Example 1:
+
+> - Paperclip orchestrates ai-agents for zero-human companies
+> - There are many types of adapters for each LLM model provider
+> - But LLM's have a context limit and not all agents can automatically compact their context
+> - So we need to have an adapter-specific configuration for which adapters can and cannot automatically compact their context
+> - This pull request adds per-adapter configuration of compaction, either auto or paperclip managed
+> - That way we can get optimal performance from any adapter/provider in Paperclip
+
+### Thinking Path Example 2:
+
+> - Paperclip orchestrates ai-agents for zero-human companies
+> - But humans want to watch the agents and oversee their work
+> - Human users also operate in teams and so they need their own logins, profiles, views etc.
+> - So we have a multi-user system for humans
+> - But humans want to be able to update their own profile picture and avatar
+> - But the avatar upload form wasn't saving the avatar to the file storage system
+> - So this PR fixes the avatar upload form to use the file storage service
+> - The benefit is we don't have a one-off file storage for just one aspect of the system, which would cause confusion and extra configuration
+
+Then have the rest of your normal PR message after the Thinking Path.
+
+This should include details about what you did, why you did it, why it matters & the benefits, how we can verify it works, and any risks.
+
+Please include screenshots if possible if you have a visible change. (use something like the [agent-browser skill](https://github.com/vercel-labs/agent-browser/blob/main/skills/agent-browser/SKILL.md) or similar to take screenshots). Ideally, you include before and after screenshots.
+
 Questions? Just ask in #dev — we're happy to help.
 
 Happy hacking!