Introduce CLAUDE.md (#1375)

### What does this PR do?

We've found the claude CLI tool is pretty helpful in this project, see
    #1372 for one example. This file is
    introduced to follow the recommendations in https://www.anthropic.com/engineering/claude-code-best-practices.

### Motivation

Tooling improvements.

Author: blt

CLAUDE.md

@@ -0,0 +1,73 @@
+# Design Goals
+
+Lading is a performance tool. It's behavior has consequences on the development
+practices of large number of engineers and so lading must be:
+
+* strictly 'faster' than targets, users must not wonder if their target has hit
+  a bottleneck or lading has,
+* deterministic, targets must receive the same load across all instances of
+  lading else replication of results is impossible and
+* extensible, lading must be available and capable of being extended for a
+  variety of use-cases.
+
+No change is valid to lading that is in conflict with these goals. In specific
+this means that lading will pre-allocate where possible, will explicitly thread
+randomness and other sources of non-determinism into code paths and will
+preference algorithms that have better worst-case behavior.
+
+# Code Style
+
+This project is subject attempts to automate code style to a great degree, using
+these tools:
+
+* `cargo clippy`
+* `cargo fmt`
+
+We do not allow for warnings: all warnings are errors. Deprecation warnings MUST
+be treated as errors. Lading is written in a "naive" style where abstraction is
+not preferred if a duplicated pattern will satisfy. Our reasoning for this is it
+makes ramp-up for new engineers easier: all you must do is follow the pattern,
+not internalize a complex type hierarchy. There are obvious places in the code
+base where replicated patterns have been made into abstractions -- we follow the
+"shape" rule, if you have three or more repeats, make a jig -- but we do not
+start there.
+
+Lading is written to be as easy to contribute to as possible. We ask that any
+dependency used in the project in more than one crate be present in the
+top-level Cargo.toml and be referenced from the workspace in sub-crates.
+
+Lading does not care about inward backward compatibility. Behavior observable to
+users must be preserved, but our internal APIs are not subject to backward
+compatibility concerns.
+
+Lading project uses comments strategically, documenting the "why" and not the
+"what". Do not add "what" comments that put into English the behavior of a line
+or two of code. Do add comments that explain the "why" of a block of code, how
+it functions or is unusual in a way that an experienced engineer might not
+understand.
+
+Crate versions are always given as XX.YY and not XX.YY.ZZ.
+
+# Testing
+
+Where possible lading prefers property tests over unit tests and in especially
+critical components we require proofs. We use
+[proptest](https://github.com/proptest-rs/proptest) in this project for property
+tests and the [kani](https://github.com/model-checking/kani) proof tool.
+
+## Workflow
+
+Changes to lading are subject this flow:
+
+* `cargo check`
+* `cargo clippy`
+* `cargo nextest run`
+
+Proofs must be run with the `cargo kani` tool in the crate where proofs reside.
+
+
+# Tools
+
+To identify outdated dependencies: `cargo outdated --root-deps-only`.
+
+To run micro-benchmarks: `cargo criterion`