ci: keep cold-cache lanes bounded

scripts/lint-shards.spec.ts

@@ -1,19 +1,31 @@
+import { readdirSync } from 'node:fs'
+import { resolve } from 'node:path'
 import { describe, expect, it } from 'vitest'
 import { selectLintShard } from './lint-shards.ts'
 
+const packagesRoot = resolve(import.meta.dirname, '..', 'packages')
+
 describe('lint gate shards', () => {
   it('keeps the unsharded local command complete', () => {
     expect(selectLintShard()).toEqual({ eslintTargets: ['.'], includeDuplication: true })
     expect(selectLintShard('')).toEqual({ eslintTargets: ['.'], includeDuplication: true })
   })
 
-  it('partitions package sources, package tests, and their repository complement', () => {
-    expect(selectLintShard('package-sources')).toEqual({
-      eslintTargets: ['packages/*/*/src/**/*.ts'],
+  it('partitions package sources and tests into alphabetic halves plus their repository complement', () => {
+    expect(selectLintShard('package-sources-a-m')).toEqual({
+      eslintTargets: ['packages/[a-m]*/*/src/**/*.ts'],
       includeDuplication: false,
     })
-    expect(selectLintShard('package-tests')).toEqual({
-      eslintTargets: ['packages/*/*/tests/**/*.ts'],
+    expect(selectLintShard('package-sources-n-z')).toEqual({
+      eslintTargets: ['packages/[n-z]*/*/src/**/*.ts'],
+      includeDuplication: false,
+    })
+    expect(selectLintShard('package-tests-a-m')).toEqual({
+      eslintTargets: ['packages/[a-m]*/*/tests/**/*.ts'],
+      includeDuplication: false,
+    })
+    expect(selectLintShard('package-tests-n-z')).toEqual({
+      eslintTargets: ['packages/[n-z]*/*/tests/**/*.ts'],
       includeDuplication: false,
     })
     expect(selectLintShard('repository')).toEqual({
@@ -28,6 +40,17 @@ describe('lint gate shards', () => {
     })
   })
 
+  it('assigns every package group to one alphabetic half', () => {
+    const groups = readdirSync(packagesRoot, { withFileTypes: true })
+      .filter(entry => entry.isDirectory())
+      .map(entry => entry.name)
+      .sort()
+    const firstHalf = groups.filter(group => /^[a-m]/u.test(group))
+    const secondHalf = groups.filter(group => /^[n-z]/u.test(group))
+
+    expect([...firstHalf, ...secondHalf].sort()).toEqual(groups)
+  })
+
   it('rejects an unknown lane', () => {
     expect(() => selectLintShard('missing')).toThrow('unknown DSH_LINT_SHARD')
   })

scripts/lint-shards.ts

@@ -19,10 +19,14 @@ export function selectLintShard(name?: string): LintSelection {
     case undefined:
     case '':
       return { eslintTargets: ['.'], includeDuplication: true }
-    case 'package-sources':
-      return { eslintTargets: ['packages/*/*/src/**/*.ts'], includeDuplication: false }
-    case 'package-tests':
-      return { eslintTargets: ['packages/*/*/tests/**/*.ts'], includeDuplication: false }
+    case 'package-sources-a-m':
+      return { eslintTargets: ['packages/[a-m]*/*/src/**/*.ts'], includeDuplication: false }
+    case 'package-sources-n-z':
+      return { eslintTargets: ['packages/[n-z]*/*/src/**/*.ts'], includeDuplication: false }
+    case 'package-tests-a-m':
+      return { eslintTargets: ['packages/[a-m]*/*/tests/**/*.ts'], includeDuplication: false }
+    case 'package-tests-n-z':
+      return { eslintTargets: ['packages/[n-z]*/*/tests/**/*.ts'], includeDuplication: false }
     case 'repository':
       return {
         eslintTargets: [