Add .agents/rules

Author: willisblackburn

.agents/rules/project.md

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+# VC83 BASIC
+
+## About the project
+
+VC83 BASIC is a BASIC interpreter written in 6502 assembly language and targeting classic 8-bit
+microcomputers such as the Apple II as well as newly-designed retrocomputers.
+
+## Coding
+
+When working on this project,
+keep in mind the very limited space available: the core interpreter needs to fit into just 8K, with
+platform-specific extensions the total size can go up to 10K, 12K, or 16K, depending on the platform.
+The specific version that must fit into 8K is the apple2 (not apple2_lc) binary. The code size limitation
+means that we may sometimes have to select algorithms that are most space-efficient, even if they are
+slower.
+
+## Testing
+
+Please run tests to verify your work, and add new tests as necessary. There are two types of tests. Unit
+tests are written in C. To run the unit tests, use `make test`. There are also functional tests that use
+the `expect` utility to send commands to the interpeter, as well as enter and run BASIC programs, and verify
+the output. Run these tests using `make expect_test`.
+Do not try to run the interpreter from the shell and interact with it; this does not work well. Use `expect` 
+either by updating or creating functional test, or run yourself from the shell.