chore(.github): add copilot-instructions

Author: benji6

.github/copilot-instructions.md

@@ -0,0 +1,47 @@
+# Copilot Instructions
+
+## Code Comments
+
+Minimize comment usage to only strictly necessary places:
+
+- **Avoid comments for self-explanatory code** - Well-named functions, variables, and clear logic should speak for themselves
+- **Use comments only when necessary** for:
+  - Complex business logic that isn't immediately obvious
+  - Non-obvious performance optimizations
+  - Workarounds for bugs in external libraries
+  - Regulatory or compliance requirements
+  - Mathematical formulas or algorithms
+
+Write code that is self-documenting through clear naming and structure rather than relying on comments.
+
+## UI Text Conventions
+
+Use **sentence case** for all UI text elements instead of Title Case. This includes:
+
+- Button labels
+- Form field labels
+- Menu items
+- Section headings
+- Error messages
+- Tooltips
+- Any other user-facing text
+
+### Examples
+
+✅ **Correct (sentence case):**
+
+- "Portfolio longevity"
+- "Safe withdrawal rates"
+- "Historical data"
+- "Calculate returns"
+
+❌ **Incorrect (Title Case):**
+
+- "Portfolio Longevity"
+- "Safe Withdrawal Rates"
+- "Historical Data"
+- "Calculate Returns"
+
+### Exception
+
+Only use title case for proper nouns and the first letter of sentences.