chore: remove repo-level .coderabbit.yaml (#139)

## Summary

- Removes the repo-level `.coderabbit.yaml` which was a template copy
overriding the org config with worse defaults
- This repo will now inherit the org-wide config from
`defi-wonderland/coderabbit`

### What was wrong with the old config

The repo-level config was a ~200-line scaffold that:
- Overrode `path_filters` with `[]` — lock files, build artifacts, and
generated code were being reviewed
- Overrode `path_instructions` with `[]` — lost all coding standard
review rules (TS, TSX, Solidity, Rust)
- Overrode `tone_instructions` with `""` — lost "focus on bugs/security"
guidance
- Overrode `auto_title_instructions` with `""` — lost conventional
commit title generation
- Set `knowledge_base.learnings.scope: auto` instead of org's `global`
- Included ~40 tool toggles that were just platform defaults

### What changes

By inheriting the org config, this repo now gets:
- Path-specific review instructions for TypeScript, React, Solidity,
Rust, tests, services, etc.
- Smart path filters excluding lock files, build artifacts, and
generated code
- Concise, security-focused review tone
- Conventional commit auto-titles
- Global knowledge base learning scope
- Reviews on PRs targeting any branch

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Author: simon-something