Copilot: move instructions to path-specific files

This is now supported. See

https://docs.github.com/en/copilot/how-tos/configure-custom-instructions/add-repository-instructions

for details.

Author: redsun82

.github/copilot-instructions.md

@@ -0,0 +1,4 @@
+---
+applyTo: "**/*.expected"
+---
+Ignore these files. These are generated to be correct by running the tests, and should not be edited by an agent.

.github/instructions/expected-files.instructions.md

@@ -0,0 +1,6 @@
+---
+applyTo: "**/*.ql,**/*.qll"
+---
+When reviewing these QL files, do not make any comment on the code itself. You don't understand the QL programming language well enough yet. You can only make comments about the following aspects:
+* comments (lines starting with `//` or block comments enclosed in `/* ... */`): you can suggest improvements to the clarity of comments, or point out spelling mistakes
+* typos in identifiers