feat(core): pass prompter through scaffoldTemplate to avoid two instances

[pyramation]

Summary

Adds an optional prompter parameter to ScaffoldTemplateOptions that gets passed through to create-gen-app's Templatizer.process(). This allows CLI tools to reuse their existing Inquirerer instance instead of create-gen-app creating a new one internally.

This eliminates the "two instances on stdin" problem that caused double-echoed keystrokes when running pgpm init workspace.

Key changes:

• Add inquirerer dependency to @pgpmjs/core for the type
• Add optional prompter field to ScaffoldTemplateOptions interface
• Pass prompter through to templatizer.process() in both local and remote template code paths
• Update workspace.ts to pass prompter instead of calling close() before scaffold

Ownership semantics: When a prompter is provided, the caller retains ownership and is responsible for closing it.

Updates since last revision

• Deleted boilerplate-scanner.ts and boilerplate-types.ts (177 lines of dead code that was exported but never used)
• Removed corresponding exports from index.ts
• Inlined the necessary helper functions (readBoilerplatesConfig, readBoilerplateConfig) directly into template-scaffold.ts

Review & Testing Checklist for Human

• CRITICAL: Verify that constructive-io/dev-utils#33 is merged first - this PR depends on it
• Test pgpm init workspace end-to-end and verify no double-echoed keystrokes occur
• Verify nothing else in the codebase was importing from the deleted boilerplate-scanner.ts or boilerplate-types.ts files
• Review the as any type assertions in template-scaffold.ts - these are temporary until create-gen-app is published with the new prompter parameter

Test plan: After merging dev-utils#33, run pgpm init workspace and verify:

1. Arrow keys work correctly (no double movement)
2. Text input doesn't echo twice
3. The workspace is created successfully

Notes

This is PR 2 of 2 in a two-PR solution. The companion PR (dev-utils#33) adds the prompter parameter to create-gen-app's API.

Link to Devin run: https://app.devin.ai/sessions/48555739db3d4f1b9e9edfa9ea1e559a
Requested by: Dan Lynch (@pyramation)

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