v2.0.1 - impact, review, security, and todos as first-class MCP tools

Four commands promoted to native Model Context Protocol tools, each with when-to-use steering: impact (what breaks if this file changes - transitive dependents and affected tests, TS/JS and pnpm-workspace aware), review (pre-commit gate; runs the repo's own eslint and tsc on JS/TS projects and merges findings), security (pre-push gate; secrets/injection audit plus pnpm audit dependency vulnerabilities), and todos (priority-ordered TODO/FIXME listing). All tool outputs are capped at 20k chars so a pathological report cannot flood agent context. Ten native tools total at ~1.1k tokens of schemas per session. 128 tests passing. See CHANGELOG.md.