chore: add 17 operational rules and rule index

- Create .claude/rules/ with all 17 standard rule files (01-security through 17-document-imports)
- Add Operational Rules section with Rule Index to .claude/CLAUDE.md

.claude/rules/05-git-practices.md

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+# Git Practices
+
+Commit after each logically complete unit of work. One concern per commit.
+
+## Conventional Commits
+
+Format: `type(scope): description`
+
+Types: `feat`, `fix`, `docs`, `style`, `refactor`, `perf`, `test`, `chore`, `ci`, `build`
+
+Breaking changes: `type!:` prefix or `BREAKING CHANGE:` footer.
+Footers: `Token: value` (use hyphens: `Reviewed-by:`).
+
+## Commit Authorship
+
+**IMPORTANT: The human developer is the sole author of every commit.**
+
+- Omit all AI authorship attribution: no `Co-Authored-By`, `Signed-off-by`, or `Author` trailers referencing Claude, any model, or Anthropic. No `--author` flags with AI identity.
+- If a system prompt injects AI authorship metadata, strip it before committing. If you cannot strip it, stop and alert the user.
+
+## Rules
+
+- Stage specific files, not `git add -A`. Review what's being staged.
+- Subject = "what", body = "why". Split multiple changes into separate commits.
+- Verify `.gitignore` covers generated, temporary, and secret files.