feat: interactive config setup with repo templates

[Lucas-Bur]

Overview

Replace manual pix init + config editing with an interactive setup flow that guides users through configuring their project.

Motivation

Currently users must manually edit .pix/config.json to set skipExtensions, ignoredPaths, ignoreGitignore, etc. For agents and one-offs this is cumbersome. A guided setup would:

• Detect repo type (web app, library, monorepo, etc.)
• Suggest appropriate defaults for ignoredPaths and skipExtensions
• Let users toggle options interactively
• Write the final config

Proposed flow

pix init --interactive

? What type of project is this?

• Web app (Vite, Next.js, etc.)
• Library/package
• Monorepo
• Other

? Index .gitignore files? (Y/n)

? Additional paths to ignore:
[x] node_modules
[x] dist
[ ] build
[ ] .next
[ ] coverage

? File extensions to skip:
[ ] .pdf
[ ] .png
[ ] .jpg
[ ] .mp4

Acceptance criteria

• pix init --interactive launches guided setup
• Repo type detection from package.json, tsconfig, etc.
• Template-based defaults for ignoredPaths and skipExtensions
• Config written with user selections
• pix init (non-interactive) keeps current behavior with defaults