feat: Add yarn workspace / yarn monorepo support (Turborepo pattern)

Summary

rtk discover shows yarn workspace as the most frequent unhandled command in my project — 194 calls in 30 days, more than find (148) or ls (179). Currently all output goes unfiltered into Claude's context.

Environment

• Package manager: yarn workspaces (Turborepo monorepo)
• Project type: TypeScript + Next.js + Fastify + Drizzle ORM
• RTK version: 0.24.0

Commands from discover output (unhandled)

Command	Count	Example
yarn workspace	194	yarn workspace api typecheck 2>&1
yarn install	12	yarn install 2>&1
yarn typecheck	2	yarn typecheck 2>&1
yarn test	2	yarn test 2>&1
yarn add	2	yarn add -D husky lint-staged

Why it matters

In a Turborepo monorepo, yarn workspace <name> typecheck 2>&1 produces large TypeScript compiler traces across multiple packages. Without filtering, every typecheck dumps full tsc output into context — same problem that rtk tsc solves for direct npx tsc calls.

Expected savings (based on rtk tsc ~11.7K tokens / 32 calls ratio): 194 yarn calls × ~365 tokens avg = ~70K tokens/month for yarn workspace alone.

Expected behavior

RTK should intercept and filter yarn commands similarly to existing handlers:

# Typecheck — route through rtk tsc filter
yarn workspace api typecheck  →  rtk tsc (errors grouped by file)

# Tests — route through rtk test filter  
yarn workspace api test       →  rtk test (failures only)
yarn test                     →  rtk test (failures only)

# Install — strip progress bars, show only errors
yarn install                  →  rtk err yarn install

# Add packages — compact output
yarn add -D husky             →  show only final installed versions

Workaround (current)

rtk err yarn workspace api typecheck
rtk test yarn workspace api test

Works but requires manual prefix — defeats the purpose of hook-based automation.

Request

1. Add yarn as a recognized command in rtk rewrite routing
2. Sub-route yarn workspace <name> typecheck → tsc filter
3. Sub-route yarn workspace <name> test / yarn test → test filter
4. Sub-route yarn install / yarn add → err filter (progress bars stripped)

Happy to test a PR — Turborepo + yarn workspaces setup available.