docs: update GEMINI setup

.gitignore

@@ -12,6 +12,7 @@ coverage.xml
 spec.json
 docker-compose.yaml
 .geminiignore
+docs/ai/ai_learnings.md
 
 # ITK Integration Test Artifacts
 itk/a2a-samples/

GEMINI.md

@@ -23,3 +23,20 @@
 1. **Required Reading**: You MUST read the contents of @./docs/ai/coding_conventions.md and @./docs/ai/mandatory_checks.md at the very beginning of EVERY coding task.
 2. **Initial Checklist**: Every `task.md` you create MUST include a section for **Mandatory Checks** from @./docs/ai/mandatory_checks.md.
 3. **Verification Requirement**: You MUST run all mandatory checks before declaring any task finished.
+
+## 5. Mistake Reflection Protocol
+
+When you realise you have made a mistake — whether caught by the user,
+by a tool, or by your own reasoning — you MUST:
+
+1. **Acknowledge the mistake explicitly** and explain what went wrong.
+2. **Reflect on the root cause**: was it a missing check, a false
+   assumption, skipped verification, or a gap in the workflow?
+3. **Immediately append a new entry to @./docs/ai/ai_learnings.md**
+   following the format defined in that file. This is not optional and
+   does not require user confirmation. Do it before continuing. Update user
+   about the changes to the workflow in the current chat.
+
+The goal is to treat every mistake as a signal that the workflow is
+incomplete, and to improve it in place so the same mistake cannot
+happen again.

docs/ai/ai_learnings.md

@@ -0,0 +1,19 @@
+> [!NOTE] for Users:
+> This document is meant to be read by an AI assistant (Gemini) in order to 
+> learn from its mistakes and improve its behavior on this project. Use
+> its findings to improve GEMINI.md setup.
+
+# AI Learnings
+
+A living record of mistakes made during this project and the rules
+derived from them. Every entry must follow the format below. 
+
+---
+
+## Entry format
+
+**Mistake**: What went wrong.
+**Root cause**: Why it happened.
+**Rule**: The concrete rule added to prevent recurrence.
+
+---