Added tsx loading for bree job workers under Vitest

[9larsons]

Extends the tsx scoping from the unified watch-mode work (#28038) so bree job workers can load Ghost's .ts server source under Vitest.

Background

#28038 scoped tsx to ghost/core's Vitest workers via require('tsx/cjs') (instead of a global NODE_OPTIONS='--import tsx', which broke the app projects). That hook is registered only in the test's own thread — it doesn't reach the worker threads bree spawns for "offloaded" jobs, so a job worker requiring .ts server source fails with Cannot find module.

This surfaced in the Phase A spike for the Mocha retirement: test/integration/jobs/update-check.test.js failed because the update-check job runs in a bree worker.

The fix

A Worker inherits the process.execArgv snapshot taken at process startup — mutating the live array does not propagate to spawned workers. So the fix:

1. Adds tsx's loader to process.execArgv.
2. Patches worker_threads.Worker so every spawned worker is passed the live execArgv explicitly.

Both are scoped to ghost/core's Vitest setup file — no effect on the app projects.

Why now

No current test hits this — no unit test offloads a .ts-loading job. But the integration and e2e suites run jobs heavily, so this unblocks migrating them off Mocha.

Testing

• test/integration/jobs/update-check.test.js (which spawns a bree job worker) now passes under Vitest.
• Full ghost/core unit suite green — 550 files / 6573 tests — confirming the Worker patch causes no regression.

[coderabbitai]

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ℹ️ Recent review info

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Run ID: 98ed22f4-dc07-4ec9-b743-4b125a8bb714

📥 Commits

Reviewing files that changed from the base of the PR and between 263ee04 and 74e29bb.

📒 Files selected for processing (1)

• ghost/core/test/utils/vitest-setup.ts

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Walkthrough

This PR adds Vitest setup code to ensure TypeScript sources can be loaded within worker threads. The change conditionally appends the tsx CommonJS loader to process.execArgv and monkey-patches the worker_threads.Worker constructor so spawned workers inherit the updated loader configuration. This prevents workers from failing when requiring Ghost's .ts files during test execution.

Possibly related PRs

• TryGhost/Ghost#27898: Modifies the same Vitest setup file to adjust test initialization.
• TryGhost/Ghost#28038: Also fixes tsx/cjs loader hook application for Vitest runs including worker-thread execution.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately describes the main change: adding tsx loading support for bree job workers in Vitest, which is the core focus of the changeset.
Description check	✅ Passed	The description is directly related to the changeset, explaining the background, the fix implementation, and testing results for the tsx loader issue in bree workers.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch vitest-bree-worker-tsx

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