Add repo-specific guidance for co-pilot (#766)

* Add repo-specific guidance for co-pilot

* Update .github/copilot-instructions.md

Co-authored-by: Davis Vaughan <[email protected]>

---------

Co-authored-by: Davis Vaughan <[email protected]>

Author: jennybc

.github/copilot-instructions.md

@@ -0,0 +1,9 @@
+Do not use `bail!`. Instead use an explicit `return Err(anyhow!(...))`.
+
+When a `match` expression is the last expression in a function, omit `return` keywords in match arms. Let the expression evaluate to the function's return value.
+
+For error messages and logging, prefer direct formatting syntax: `Err(anyhow!("Message: {err}"))` instead of `Err(anyhow!("Message: {}", err))`.
+
+Use `log::trace!` instead of `log::debug!`.
+
+Use fully qualified result types (`anyhow::Result`) instead of importing them.