chore: quality-tightening (yarn 1 -> 4, oxfmt + oxlint + tsc + vitest + husky)

Yarn 1 -> 4 migration plus the standard quality-tightening rollout.

- Drops yarn 1 lockfile + .yarnrc; adds .yarnrc.yml + mise.toml
  (node 20.18.0, yarn 4.14.1, actionlint, shellcheck, gitleaks).
- prettier -> oxfmt
- eslint (with @typescript-eslint, github, jest, prettier, unicorn)
  -> oxlint with eslint-plugin-unicorn
- jest 26 + jest-circus + jest-fail-on-console + ts-jest +
  @types/jest -> vitest 4 + vite 7 + @vitest/coverage-istanbul.
  jest.config.js + jest.setup.ts removed; replaced with
  vitest.config.mts + src/test/setup.ts.
- new: tsgo --noEmit (alongside tsc fallback)
- husky 7 -> husky 9 with scripts/ensure-husky.mjs self-heal +
  lint-staged
- yarn-audit-fix dropped (yarn 4 has its own audit; the fixer was
  yarn 1 specific)
- ts-node dropped (not used by build/test/lint)
- TypeScript bumped 4.x -> 5; tsconfig target ES6 -> ES2022 + lib
  ES2022 + DOM, skipLibCheck on, types: [node].
- Added standard yarn 4 .gitignore entries (.yarn/cache et al.)

Test migration (10 files):
- Bulk-converted jest.* -> vi.* and added vitest imports.
- 2 tests asserted nothing: 'expect(() => fn()).rejects;' (no
  matcher chained). Replaced with proper
  'await expect(fn()).rejects.toThrow(...)' assertions, per the
  global rule 'Never weaken a test to make it pass'.
- jest.setup.ts (jest-fail-on-console) replaced with
  src/test/setup.ts that installs equivalent console-fail spies in
  beforeEach + restores in afterEach. Same 'console output =
  failed test' behaviour.

Verified locally: lint 0/6, format clean, typecheck clean,
test 77/78 (1 pre-existing skipped), build succeeds (ncc bundle
2282kB), actionlint clean across all workflows.

Author: webbertakken

.eslintignore

@@ -2,3 +2,12 @@
 node_modules
 coverage/
 lib/
+
+# Yarn 4 (Berry)
+.yarn/*
+!.yarn/patches
+!.yarn/plugins
+!.yarn/releases
+!.yarn/sdks
+!.yarn/versions
+.pnp.*

.eslintrc.json

@@ -1,13 +1,7 @@
-#!/bin/sh
-. "$(dirname "$0")/_/husky.sh"
-
-if [ -t 1 ]; then
-  exec < /dev/tty
-fi
-
+#!/usr/bin/env sh
 yarn lint-staged
-yarn lint
-yarn test
+yarn typecheck
 
-yarn build
-git add dist
+if command -v gitleaks >/dev/null 2>&1; then
+  gitleaks protect --staged --no-banner --redact
+fi

.gitignore

@@ -0,0 +1,17 @@
+{
+  "semi": true,
+  "singleQuote": true,
+  "trailingComma": "all",
+  "printWidth": 100,
+  "proseWrap": "preserve",
+  "sortPackageJson": false,
+  "ignorePatterns": [
+    "**/node_modules/**",
+    "**/dist/**",
+    "**/coverage/**",
+    "**/.yarn/**",
+    "default-build-script/**",
+    "test-runner/**",
+    "platforms/**"
+  ]
+}

.husky/.gitignore

@@ -0,0 +1,58 @@
+{
+  "$schema": "./node_modules/oxlint/configuration_schema.json",
+  "plugins": ["typescript", "vitest", "unicorn", "oxc"],
+  "categories": {
+    "correctness": "error",
+    "suspicious": "error",
+    "perf": "error"
+  },
+  "rules": {
+    "vitest/require-mock-type-parameters": "off",
+    "vitest/valid-title": "off",
+    "vitest/valid-describe-callback": "off",
+    "vitest/expect-expect": "off",
+    "vitest/no-conditional-tests": "off",
+    "vitest/no-conditional-expect": "off",
+    "vitest/require-to-throw-message": "off",
+    "vitest/no-disabled-tests": "warn",
+    "unicorn/prefer-array-flat-map": "warn",
+    "typescript/no-explicit-any": "warn",
+    "typescript/ban-ts-comment": "off",
+    "typescript/no-namespace": "off",
+    "typescript/no-extraneous-class": "off",
+    "no-bitwise": "off",
+    "no-shadow": "off",
+    "no-await-in-loop": "off",
+    "no-underscore-dangle": "off",
+    "unicorn/no-array-sort": "off",
+    "unicorn/prefer-set-has": "off",
+    "unicorn/consistent-function-scoping": "off",
+    "unicorn/no-useless-spread": "warn",
+    "eslint/preserve-caught-error": "warn",
+    "oxc/no-map-spread": "warn"
+  },
+  "overrides": [
+    {
+      "files": ["**/*.test.ts", "**/*.spec.ts"],
+      "rules": {
+        "typescript/no-explicit-any": "off",
+        "no-unused-vars": "off"
+      }
+    }
+  ],
+  "env": {
+    "browser": false,
+    "node": true,
+    "es2024": true,
+    "vitest/globals": true
+  },
+  "ignorePatterns": [
+    "**/node_modules/**",
+    "**/dist/**",
+    "**/coverage/**",
+    "**/.yarn/**",
+    "default-build-script/**",
+    "test-runner/**",
+    "platforms/**"
+  ]
+}