refactor(auditor): split rules into smaller modules

[Orchardxyz]

Summary

Refactor crates/hk-core/src/auditor/rules.rs into a directory-based module layout for better readability and long-term maintainability.

This change keeps behavior unchanged while breaking a large file into
smaller focused modules:

• content.rs
• permissions.rs
• cli.rs
• mcp.rs
• plugin.rs
• shared.rs
• test_support.rs

The rules.rs file remains the public entrypoint and still assembles
all_rules() in the same order.

Motivation

rules.rs had grown large enough to be harder to navigate and review. Splitting it into smaller modules makes the audit rules easier to maintain, extend, and test over time.

Verification

• Run cargo test -p hk-core auditor --locked
• Run npm test -- src/pages/__tests__/audit-utils.test.ts

Notes

This PR is intended as a structural refactor only.
No functional changes are intended.

[RealZST]

Merged. Thanks!