fix(hookify): match Write and prompt rules

[ShiroKSH]

Summary

• Make file rules inspect content passed to Write as new text.
• Map simple prompt rules to the current UserPromptSubmit payload and retain the legacy configured field.
• Add regression coverage for Write, Edit, and prompt rules.

Root cause

Simple rules were inferred as fields absent from normal Write and UserPromptSubmit payloads, so documented Hookify rules silently did not match.

Validation

• Ran the Hookify unittest discovery suite: 4 tests passed.
• Ran Python bytecode compilation for Hookify.
• Parsed the writing-rules skill frontmatter as YAML.
• Ran git diff whitespace validation.