Redesign install.sh onboarding to be repo-agnostic

[guodong-sq]

Replace hardcoded java-monorepo defaults with a user-centric flow that:

• Asks which repository to manage first
• Auto-detects default branch from origin/HEAD or main/master
• Derives all paths from repo location (e.g., myrepo -> myrepo-master, myrepo-worktrees)
• Shows derived config and allows customization

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  Repository Setup
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Which repository do you want to manage with worktrees?

Enter the path to your existing git repository.
Example: ~/Development/myrepo

Repository path: ~/Development/java             <--- user input

Detected repository:
  Path:   /Users/guodong/Development/java
  Remote: [remote-ssh-path]
  Branch: master (default branch)

Derived configuration:

  The worktree toolkit will set up the following structure:

  Active symlink:      /Users/guodong/Development/java
     Your IDE opens this path. It's a symlink that can point to any worktree.

  Main repository:     /Users/guodong/Development/java-master
     Your current repo will be moved here (the "master" worktree).

  Worktrees directory: /Users/guodong/Development/java-worktrees
     New worktrees will be created here.

  IntelliJ metadata:   /Users/guodong/.config/wt/idea-files/java
     Shared .ijwb files for instant project switching.

  Default branch:      master
     Used when creating new worktrees.

Use this configuration? [Y/n] n               <--- user input

You can customize each value. Press Enter to keep the default.

Active symlink path [/Users/guodong/Development/java]:
...

[HamptonMakes]

So I was wondering. if it shoudl be like...

java/base
java/worktrees/blah
java/java

[HamptonMakes]

love this.

[guodong-sq]

So I was wondering. if it shoudl be like...

java/base java/worktrees/blah java/java

we could skip auto-deriving paths entirely and just prompt for each path individually. That way users can choose whichever structure fits their setup. What do you think?