feat: configure jest for esm dependency compatibility

[Copilot]

Jest cannot parse ESM-only packages, blocking dependency updates (chalk 5.x, execa 9.x, commander 14.x). This adds Babel transformation to handle ESM→CJS conversion in tests.

Changes

• babel.config.js: New Babel config with @babel/preset-env targeting current Node.js
• jest.config.js: Added babel-jest transformer for JS files and transformIgnorePatterns to transform chalk|execa|commander in node_modules
• jest.integration.config.js: Applied same ESM transformation config for integration tests
• package.json: Added @babel/core, @babel/preset-env, babel-jest dev dependencies
• jest-esm-config.test.ts: Test suite validating ESM transformation works correctly
• TESTING.md: Documented ESM module support

Scope

Fixes Jest's ability to parse ESM modules. Does not address API breaking changes in execa/commander upgrades - those require separate source modifications.

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Original prompt

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This section details on the original issue you should resolve

<issue_title>[DevTools] Configure Jest for ESM dependency compatibility</issue_title>
<issue_description>## Background

PR #289 proposed adding ESM support to the Jest configuration to fix CI failures when updating ESM-only dependencies.

Problem

Dependency PRs (chalk 5.x, execa 9.x, commander 14.x, etc.) fail CI because Jest cannot parse ESM-only packages.

Proposed Changes

• jest.config.js: Add transformIgnorePatterns to transform chalk and babel-jest for JS files
• babel.config.js: New Babel config targeting current Node.js for ESM→CJS transformation
• package.json: Add @babel/core, @babel/preset-env, babel-jest as dev dependencies

Expected Results

Dependency	Before	After
chalk 4→5	❌ Jest ESM error	✅ Fixed
execa 5→9	❌ API changes	❌ Needs code updates
commander 12→14	❌ Stricter args	❌ Needs code updates

Notes

PRs for execa and commander have breaking API changes requiring source modifications—those cannot be fixed through configuration alone.

---

Issue created from PR #289 during backlog cleanup</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes [DevTools] Configure Jest for ESM dependency compatibility #421

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✅ Coverage Check Passed

Overall Coverage

Metric	Base	PR	Delta
Lines	77.98%	77.98%	➡️ +0.00%
Statements	78.05%	78.05%	➡️ +0.00%
Functions	77.77%	77.77%	➡️ +0.00%
Branches	71.70%	71.70%	➡️ +0.00%

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Coverage comparison generated by scripts/ci/compare-coverage.ts

[github-actions]

Smoke Test Results ✅

Last 2 Merged PRs:

• docs: add agent image tooling reference #426: docs: add agent image tooling reference
• fix(deps): update js-yaml to 3.14.2 (CVE fix) #424: fix(deps): update js-yaml to 3.14.2 (CVE fix)

Test Results:

• ✅ GitHub MCP: Retrieved PR data
• ✅ Playwright: Page title verified ("GitHub · Change is constant. GitHub keeps you ahead. · GitHub")
• ✅ File Write: Created /tmp/gh-aw/agent/smoke-test-copilot-21379016620.txt
• ✅ Bash Tool: File verified successfully

Overall Status: PASS

cc: @Copilot @Mossaka

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[github-actions]

Smoke Test Results - Claude

Last 2 merged PRs:

• docs: add agent image tooling reference #426: docs: add agent image tooling reference
• fix(deps): update js-yaml to 3.14.2 (CVE fix) #424: fix(deps): update js-yaml to 3.14.2 (CVE fix)

✅ GitHub MCP: Retrieved PR data
✅ Playwright: Navigated to github.com, title verified
✅ File Writing: Created test file
✅ Bash Tool: File contents verified

Overall Status: PASS

AI generated by Smoke Claude