Fixes, performance improvements and new benchmarks

.gitignore

@@ -2,3 +2,5 @@
 .vscode/
 scratch*
 .ipynb_checkpoints/
+flamegraph.svg
+perf.data

AGENTS.md

@@ -1,4 +1,31 @@
 # Agent Instructions
 
-- use `cargo fmt`, `cargo clippy` and `cargo test`
-- only commit when all these checks are passing
+## Development Workflow
+
+* This is a Rust project, ALWAYS use `cargo fmt`, `cargo clippy` and `cargo test` and fix issues.
+* When the code is formatted, linted and successfully tested, ALWAYS commit your changes.
+
+## Agent Behavior
+
+* ALWAYS ask if there is any ambiguity in the request or multiple viable solutions.
+* NEVER guess, think through issues, read docs and existing code, discuss with the user.
+* NEVER assume anything if you are not confident or need more details.
+* If documentation is missing, try installing it or ask the user for help.
+
+## Code Quality
+
+* Avoid data duplication: NEVER hardcode a numeric value or string in two places, define constants.
+* Avoid code duplication: NEVER write the same logic twice, factor out a common generic function.
+
+* Before writing any new non-trivial code, ALWAYS check whether similar functionality already exists.
+* Before writing any new non-trivial code, ALWAYS consider using existing popular third-party crates.
+* When actually writing new code, ALWAYS try to write it in a reusable and extensible way from the start.
+
+* ALWAYS strive towards generic, modular, maintainable code.
+* ALWAYS prioritize good architecture and clarity over performance unless told otherwise..
+* ALWAYS write testable code with easily mockable inputs.
+* ALWAYS write small functions that ideally fit on a single screen.
+* ALWAYS avoid deep nesting, use more helper functions instead.
+* ALWAYS ask for permission to let a function be untested.
+* ALWAYS plan out suitable tests for the intended design BEFORE implementation.
+* ALWAYS strive to test all code paths, covering edge cases and boundary input values.