fix: Be more explicit about coding quality

By making the AGENTS.md file more explicit about the code quality
standards, it will hopefully result in cleaner code.

There was a tendency to mask unused variables by prefixing them with a _
instead of removing them. That is not what I want: if it's unused, I
want it gone.

AGENTS.md

@@ -137,6 +137,7 @@ mod tests {
 - Keep core business logic separate from external integrations
 - Use workspace dependencies consistently
 - When working from a spec, update the spec with the current status as soon as you finish something
+- **MANDATORY**: After making ANY code change, complete the Post-Change Verification Checklist (see Code Quality section below)
 
 ### 2. Testing
 - Write tests alongside code in `#[cfg(test)]` modules
@@ -149,9 +150,20 @@ mod tests {
 - Use `cargo fmt` for formatting
 - Use `cargo clippy` for linting
 - Ensure documentation for public APIs
-- _ALWAYS_ format and lint after making a change, and fix linting errors and warnings
+- **MANDATORY: ALWAYS format and lint after making ANY change, and fix ALL linting errors and warnings**
 - When a change is end-user visible, update the README.md. Use the README.md documentation guidelines
-- Always clean up unused code. No todo's or unused code is allowed after a change
+- Always clean up unused code. No todo's or unused code is allowed after a change. Remove unused variables, functions, imports, etc. Do NOT hide unused code with underscores - delete it!
+
+#### Post-Change Verification Checklist (MANDATORY)
+After making ANY code change, you MUST run these commands and fix any issues:
+
+1. **Format code**: `cargo fmt --all`
+2. **Run linter**: `cargo clippy --all-targets --all-features -- -D warnings`
+3. **Run tests**: `cargo test --workspace`
+4. **Build project**: `cargo build --workspace`
+5. **Clean up unused code**: Remove any unused variables, functions, imports, etc.
+
+**FAILURE TO COMPLETE THIS CHECKLIST WILL RESULT IN CODE REJECTION**
 
 ### 4. Commit Standards
 - *Always* ensure the workspace compiles: `cargo build --workspace`