[Blueprints][installTheme step] Honor ifAlreadyInstalled for directory themes

[adamziel]

What it does

Makes directory-based installTheme resources honor the existing ifAlreadyInstalled option.

ifAlreadyInstalled	Directory theme behavior
overwrite	Replace the existing theme directory.
skip	Keep the existing theme directory and continue.
error	Throw before writing files.

Rationale

Zip-based theme installs already respect ifAlreadyInstalled, but directory resources always rewrote the target directory through writeFiles(..., { rmRoot: true }).

Blueprint v2 lowering uses directory resources, so it needs the same collision semantics as zip resources before the runner can rely on this step consistently.

Implementation

Before writing directory-resource theme files, installTheme() now checks whether the target directory already exists and applies the same ifAlreadyInstalled rule used by zip installs.

This PR intentionally does not add path validation or symlink hardening. Those are separate behaviors and should stay reviewable on their own.

Testing instructions

Validated locally:

npm run format:uncommitted
npm exec nx run playground-blueprints:test:vite -- --testFiles=packages/playground/blueprints/src/tests/steps/install-theme.spec.ts
npm exec nx run playground-blueprints:lint
npm exec nx run playground-blueprints:typecheck
git diff --check

[Copilot]

Pull request overview

Note

Copilot was unable to run its full agentic suite in this review.

Updates the installTheme blueprint step so directory-based theme installs honor the ifAlreadyInstalled collision behavior (matching zip-based installs), and adds a test covering skip/overwrite/error.

Changes:

• Apply ifAlreadyInstalled semantics when installing directory theme resources (skip, overwrite, error).
• Add a spec that exercises the new directory-theme collision behavior.

Reviewed changes

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

File	Description
packages/playground/blueprints/src/lib/steps/install-theme.ts	Adds collision handling before writing directory theme files to honor ifAlreadyInstalled.
packages/playground/blueprints/src/tests/steps/install-theme.spec.ts	Adds coverage for directory-theme installs respecting skip/overwrite/error.

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