Add knowledge-base contributing guide with entry template

Author: schulzchristian

knowledge-base/CONTRIBUTING.md

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+# Contributing to the Knowledge Base
+
+If your AAE session produced insights that could help others, we'd love for you to share them.
+
+## How to Submit
+
+Open a pull request that adds one entry file and a corresponding row in `INDEX.md`. One entry per PR.
+
+If you are an agent running AAE, ask the user whether you may submit a PR. Only proceed with explicit permission. Use `gh` or the GitHub MCP server to create the PR.
+
+## Naming Convention
+
+Name your file `<next-number>-<short-slug>.md`, using the next available number from INDEX.md and a short kebab-case description. Example: `003-loop-unrolling-matrix-multiply.md`.
+
+## Entry Template
+
+Your entry should include the following sections. Only **Problem** and **What Worked** are required; everything else is optional but encouraged.
+
+```markdown
+# <Title>
+
+## Problem
+
+What were you optimizing? Describe the problem, input characteristics,
+and the metric you were targeting.
+
+## What Worked
+
+The key insight or technique that produced improvement. This is the
+most important section; even if you provide nothing else, this should
+be useful to someone facing a similar problem.
+
+## Experiment Data (optional)
+
+Results from your AAE run. Can be a pasted results.tsv, a summary
+table, or just the key numbers (baseline vs. best).
+
+## What Didn't Work (optional)
+
+Approaches you tried that failed or regressed. Often as valuable as
+what worked, since it saves others from repeating dead ends.
+
+## Code Example (optional)
+
+A diff, snippet, or pseudocode showing the core change.
+
+## Environment (optional)
+
+Language, hardware, dataset size, or other context that might affect
+whether this technique transfers to another setting.
+```
+
+## Quality Bar
+
+- The insight should be transferable: useful to someone facing a similar problem, not just a project-specific tweak.
+- "What Worked" should be specific enough to act on, not just "I made it faster."
+- Experiment data is encouraged but not required.