build: update action runtime to Node.js 24

[adam0white]

GitHub Actions is deprecating Node.js 20, with Node 24 becoming the default
runner on June 2, 2026. This updates setup-bun to run on the Node 24 runtime.

Changes:

• action.yml: node20 → node24
• esbuild target: node20 → node24
• @types/node: ^20 → ^24
• @actions/* deps bumped to their Node 24-compatible versions (highest CJS-compatible releases, avoiding the ESM-only latest)

Notes:

• The @actions/* packages were pinned to the highest CJS-compatible versions (core@2, cache@5, tool-cache@3, etc.) since esbuild outputs CJS. The next majors (core@3, cache@6) are ESM-only.
• Other actions (checkout, cache, setup-node) shipped this as a new major.

The @actions/* bumps also resolve the punycode deprecation warning (DEP0040) that Node 24 triggers with the older dependency chain.

Closes #172
Related: #173, #174, #175

Test plan

• bun test — 56 pass, 6 pre-existing fail (same as main)
• bun run build — reproducible (identical checksums on rebuild)
• bun run format — all files unchanged
• Source audit: zero Node 24 deprecated APIs in use
• CI matrix (ubuntu/macos/windows) validates on PR 🤞

[coderabbitai]

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📥 Commits

Reviewing files that changed from the base of the PR and between ecf28dd and 57c4f23.

⛔ Files ignored due to path filters (3)

• bun.lock is excluded by !**/*.lock
• dist/cache-save/index.js is excluded by !**/dist/**
• dist/setup/index.js is excluded by !**/dist/**

📒 Files selected for processing (2)

• action.yml
• package.json

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Walkthrough

Updated GitHub Actions runner image and build script from Node.js 20 to 24. Upgraded @actions/* dependencies and @types/node devDependency to newer major versions compatible with Node.js 24 runtime.

Changes

Cohort / File(s)	Summary
Node.js Runtime Upgrade action.yml, package.json	Updated GitHub Actions runner image from node20 to node24; updated build script target from Node.js 20 to 24.
Action Packages package.json	Upgraded @actions/* dependencies (@cache, @core, @exec, @glob, @io, @tool-cache) to newer major versions for Node.js 24 compatibility.
Type Definitions package.json	Updated @types/node devDependency from ^20.x to ^24.x.

🚥 Pre-merge checks | ✅ 4

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title 'build: update action runtime to Node.js 24' directly and clearly summarizes the main change of updating the GitHub Actions runner from Node.js 20 to Node.js 24.
Description check	✅ Passed	The description provides comprehensive context about the Node.js 20 deprecation, explains the migration to Node.js 24, lists all changes made, and includes testing details directly related to the changeset.
Linked Issues check	✅ Passed	The PR addresses the primary objective of #172 by migrating the GitHub Actions runtime from Node.js 20 to Node.js 24, including updates to action.yml, build configuration, and dependencies.
Out of Scope Changes check	✅ Passed	All code changes are directly related to the Node.js 24 migration objective: action.yml runtime update, esbuild target update, @types/node update, and @actions/* dependency upgrades for Node 24 compatibility.

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[xhyrom]

LGTM