[zjw1111]

Purpose

Linked issue: N/A (documentation-only change).

Coding conventions and contribution workflow are currently mixed in the code style guide, while several design and testing expectations are implicit. This change gives each topic a primary home:

• Clarify parameter ordering, output and input/output pointers, ownership, initialization, comments, and test macros in the code style guide.
• Add development guidelines for defaults, abstraction, dependencies, return semantics, validation boundaries, and effective regression coverage. Keep defensive checks, overflow tests, and mock interaction assertions proportionate to reachable risks and required behavior.
• Consolidate setup, validation commands, and the PR checklist in CONTRIBUTING.md, document external code attribution, and update the shared guidance links in AGENTS.md.

Tests

No tests are added or modified because this change only updates contributor documentation and does not change runtime behavior.

API and Format

No changes to public APIs, storage formats, or protocols.

Documentation

Updates CONTRIBUTING.md, docs/code-style.md, and AGENTS.md; adds docs/development-guidelines.md.

Generative AI tooling

Generated-by: Codex CLI 0.163.0