feat(yarn): add yarn command support with smart delegation

[jzambrano12]

Summary

• Add yarn_cmd.rs module following the npm_cmd.rs flat-args pattern with run injection logic and YARN_SUBCOMMANDS list (35 known subcommands)
• Smart routing: auto-detect known tools (vitest, tsc, eslint, biome, next, prettier, playwright) and delegate to existing specialized RTK filters for maximum savings (up to 99%)
• Generic filter strips Yarn Classic v1 boilerplate (yarn run vX.Y.Z, $ cmd, Done in Xs) and Berry v2+ info lines (YN0000:)
• Specialized install filter strips progress phases ([1/4]...), info/warning lines (75% reduction)
• Register Yarn variant in Commands enum, routing, and operational command list in main.rs
• Add discover/rewrite rules: yarn pattern + rule with per-subcommand savings estimates
• Add yarn\s+ prefix to 7 existing tool patterns (tsc, lint, prettier, next, vitest, playwright, prisma) so yarn tsc, yarn vitest, etc. are recognized by discover

Motivation

rtk discover on a real project (615 sessions, 30 days) shows 126+ unhandled yarn commands:

yarn build          58 uses
yarn lint           19 uses
yarn check          17 uses
yarn vitest         14 uses
yarn tsc             9 uses
yarn validate-translations  9 uses

Token Savings

Command	Strategy	Expected Savings
yarn vitest	Delegate to vitest_cmd	99%
yarn build	Delegate to next_cmd or generic filter	85%
yarn lint	Delegate to lint_cmd	84%
yarn tsc	Delegate to tsc_cmd	83%
yarn install	Specialized install filter	75%
yarn check	Generic filter	65%
Custom scripts	Generic boilerplate strip	10-40%

Test Plan

• 35 yarn-specific tests passing (cargo test yarn → 35 passed)
• Full suite: 1149 tests passing, 0 clippy errors, clean fmt
• Unit tests: filter output, edge cases (ANSI, unicode, errors, Berry format, malformed input)
• Token savings assertions (≥55% for install, ≥10% for generic)
• Subcommand routing: all 35 YARN_SUBCOMMANDS verified, discover commands verified
• Registry tests: rewrite/classify for yarn build, install, lint, tsc, vitest, check, add, compound, redirect
• Smoke tests: help, --help, --version (conditional), --skip-env
• cargo fmt --all --check && cargo clippy --all-targets && cargo test passes

Files Changed

File	Action	Lines
src/yarn_cmd.rs	NEW	+479 (module + 35 tests)
src/main.rs	EDIT	+13 (mod, enum, routing)
src/discover/rules.rs	EDIT	+41 (patterns, rules, prefixes)
src/discover/registry.rs	EDIT	+125 (12 rewrite/classify tests)
scripts/test-all.sh	EDIT	+12 (smoke tests)
CHANGELOG.md	EDIT	+5 (feature entries)
README.md	EDIT	+1 (command table)

[CLAassistant]

All committers have signed the CLA.

[aeppling]

Hey

We are cleaning up the codebase and improving the project structure for better onboarding. As part of this effort, PR #826 reorganizes src/ from a flat layout into subfolders.

No logic changes — only file moves and import path updates.

What you need to do

Rebase your branch on develop when receiving this comment:

git fetch origin && git rebase origin/develop

Git detects renames automatically. If you get import conflicts, update the paths:

use crate::git;        // now: use crate::cmds::git::git;
use crate::tracking;   // now: use crate::core::tracking;
use crate::config;     // now: use crate::core::config;
use crate::init;       // now: use crate::hooks::init;
use crate::gain;       // now: use crate::analytics::gain;

Need help rebasing? Tag @aeppling

[jzambrano12]

Hey

We are cleaning up the codebase and improving the project structure for better onboarding. As part of this effort, PR #826 reorganizes src/ from a flat layout into subfolders.

No logic changes — only file moves and import path updates.

What you need to do

Rebase your branch on develop when receiving this comment:

git fetch origin && git rebase origin/develop

Git detects renames automatically. If you get import conflicts, update the paths:

use crate::git;        // now: use crate::cmds::git::git;
use crate::tracking;   // now: use crate::core::tracking;
use crate::config;     // now: use crate::core::config;
use crate::init;       // now: use crate::hooks::init;
use crate::gain;       // now: use crate::analytics::gain;

Need help rebasing? Tag @aeppling

Done!