feat: handle user style existence

[Mister-Hope]

Ecosystem is planning to decouple user style logic from palette plugins, so now user style file updates should be handled in core.

[coveralls]

Coverage Report for CI Build 25589227347

Coverage decreased (-1.1%) to 72.664%

Details

• Coverage decreased (-1.1%) from the base build.
• Patch coverage: 17 uncovered changes across 3 files (2 of 19 lines covered, 10.53%).
• No coverage regressions found.

Uncovered Changes

File	Changed	Covered	%
packages/cli/src/commands/dev/watchUserStyleFile.ts	9	1	11.11%
packages/core/src/app/prepare/prepareUserStyle.ts	8	1	12.5%
packages/cli/src/commands/dev/dev.ts	2	0	0.0%

Coverage Regressions

No coverage regressions found.

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Coverage Stats

Relevant Lines:	1053
Covered Lines:	762
Line Coverage:	72.36%
Relevant Branches:	520
Covered Branches:	381
Branch Coverage:	73.27%
Branches in Coverage %:	Yes
Coverage Strength:	43.89 hits per line

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💛 - Coveralls

[Copilot]

Pull request overview

This PR refactors how userStyle is injected into the client bundle by generating a dedicated internal temp module (@internal/userStyle) and importing it from the client entry, while also adding a dev watcher to update that temp module when the style file is created or deleted.

Changes:

• Add prepareUserStyle() to generate internal/userStyle.js only importing the user style when the file exists.
• Switch the client entry to always import @internal/userStyle, and remove the previous userStyle import injection from the client-configs temp entry.
• Add a dev-mode watcher to re-generate the user-style temp module on add/unlink events.

Reviewed changes

Copilot reviewed 8 out of 9 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
packages/core/src/app/prepare/prepareUserStyle.ts	New temp file generator for @internal/userStyle, with existence check.
packages/core/src/app/prepare/prepareClientConfigs.ts	Removes prior userStyle import injection from the client-configs entry.
packages/core/src/app/prepare/index.ts	Exports the new prepareUserStyle() helper.
packages/client/src/types/internal/userStyle.d.ts	Adds type declaration for the new @internal/userStyle module.
packages/client/src/app.ts	Adds side-effect import of @internal/userStyle from the client entry.
packages/cli/src/commands/dev/watchUserStyleFile.ts	New chokidar watcher to re-run prepareUserStyle() on style file add/unlink.
packages/cli/src/commands/dev/index.ts	Exports the new watcher helper.
packages/cli/src/commands/dev/dev.ts	Registers the user-style watcher when app.options.userStyle is set.

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