fix: validate --path flag is a directory, not a file

[byrichardpowell]

Summary

• Adds isDirectorySync() validation to the --path flag in theme commands
• Shows a clear error message with a "Did you mean:" suggestion pointing to the parent directory
• Adds return before process.exit(1) calls for safety when process.exit is mocked in tests

Problem

The --path flag in all theme commands (theme check, theme dev, theme push, etc.) validated that the provided path existed using fileExistsSync(), but did not check whether it was a directory. Since fileExistsSync() returns true for both files and directories, users could pass a file path like sections/foo.liquid and the validation would accept it.

Downstream, @shopify/theme-check-node's loadConfig() calls fs.readdir(root) on the path, which throws ENOTDIR: not a directory, scandir when the path is a file.

Impact: ~490 error events across 220+ affected users in the last 7 days (first seen in CLI 3.93.0).

The errors appear across all platforms (macOS, Windows, Linux) and affect many different theme files (sections/*.liquid, snippets/*.liquid, templates/*.json, blocks/*.liquid, locales/*.json). The likely cause is IDE integrations or editor tasks that pass the currently open file as the --path argument.

Related issue: https://github.com/shop/issues/issues/33774
Observe dashboard: https://observe.shopify.io/a/observe/errors/13708469716602397840

Test plan

• New test: verifies error message when a file path is passed to --path
• Existing test: verifies error message when a non-existent path is passed
• Existing test: verifies directory paths are accepted
• All 565 theme tests pass (58 test files)
• check.test.ts tests pass (these mock process.exit and use fake paths)
• Lint and type checks pass

🤖 Generated with Claude Code

[Copilot]

Pull request overview

Improves validation for the --path flag in theme commands to prevent passing file paths (which can lead to ENOTDIR errors downstream) and adds/updates tests and release notes.

Changes:

• Validate that --path exists and is a directory; otherwise render a clearer error (with a parent-directory suggestion) and exit.
• Add a test covering the “file path provided” case and fix minor test wording typos.
• Add a changeset documenting the patch release.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
packages/theme/src/cli/flags.ts	Adds directory validation and improved error output for invalid --path values.
packages/theme/src/cli/flags.test.ts	Adds coverage for passing a file path; fixes test description typos.
.changeset/fix-theme-check-path-file-validation.md	Documents the patch change in release notes.

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