Detect and redirect when mcs sync runs from ~/.claude

[bguidolim]

Problem

Users trying to install packs globally cd ~/.claude && mcs sync instead of running mcs sync --global from anywhere. This is broken:

• ~/.claude is a real directory, so SyncCommand proceeds as if it were a project root.
• ProjectDetector walks up, potentially latching onto weird state or creating ~/.claude/.claude/ garbage.
• Nothing tells the user they took the wrong path — they may believe the install succeeded.

Proposed solution

1. Detect ~/.claude as cwd and redirect

At the start of SyncCommand.perform() (or inside performProject), resolve the effective target path. If it's env.claudeDirectory or anywhere under it, and --global wasn't passed:

It looks like you want to sync global scope.
Use 'mcs sync --global' instead? [Y/n]

• Yes → set global = true internally, chdir to env.homeDirectory to keep ProjectDetector well-behaved, then proceed.
• No → hard error with the same suggestion in the message.

If --global is passed but cwd happens to be ~/.claude, silently chdir to $HOME before running — no prompt, just avoid the footgun.

2. Scope picker on bare mcs sync (bonus, same root cause)

When mcs sync runs with no --global / --pack / --all flags and ProjectDetector fails to find a project root (no .git/, no CLAUDE.local.md), show a scope picker before the pack picker:

Where to sync?
  > This directory (./)
    Global (~/.claude)

This kills the cd ~/.claude instinct at the root — users never need to "go somewhere" to configure globally.

Tradeoff

Pure block (error-only) is simpler but less helpful — users who get the error often retry the wrong thing. Offering the right command inline (with a confirmation prompt) converts confusion into learning. Auto-redirect without prompt is friendlier but surprising; explicit confirmation keeps intent clear.

Scope

Sources/mcs/Commands/SyncCommand.swift — add a cwd guard at the top of perform(), before performGlobal / performProject branch. Uses existing Environment.claudeDirectory for the comparison.