Feature Request: dwell sync command + remote repo setup in dwell init

[grave0x]

Summary

Add a dwell sync command that auto-commits changes and pushes to the configured git remote. Also add remote repo setup during dwell init so the user can provide a remote URL upfront.

Motivation

Currently dwell init creates a local git repo but does not configure a remote. Users must manually run git remote add and git push after adding dotfiles. There is also no command to auto-commit and push changes — users must shell out to git manually.

Proposed behavior

1. dwell init — remote repo setup

Extend dwell init to accept a --remote flag:

dwell init                                         # local only (current behavior)
dwell init --remote https://github.com/user/dotfiles.git   # + set up origin
dwell init --remote git@github.com:user/dotfiles.git       # SSH
dwell init --clone https://github.com/user/dotfiles.git    # existing (works)

When --remote is provided:

• Create/init the local repo as before
• Set origin to the provided URL
• Optionally do an initial push

2. dwell sync — commit and push

dwell sync                              # auto-commit + push
dwell sync -m "Custom commit message"   # with message
dwell sync --dry-run                    # preview what would be committed

The sync command should:

• Stage all changed files in the source directory (git add -A)
• Commit changes with a descriptive auto-message (or custom via -m)
• Push to the configured remote

Auto-commit message format: "dwell: sync [N] file(s) — [YYYY-MM-DD HH:MM]" or use the custom message.

3. dwell status — show git sync status

Extend dwell status (or add dwell status --sync) to show:

• Whether the source directory has a remote configured
• Whether there are uncommitted changes
• Whether the local branch is ahead/behind the remote
• Last sync timestamp

Implementation notes

• GitRepo in dwell-store already has add(), commit(), status_summary() methods
• Need to add: remote_url(), has_remote(), push(), is_ahead(), is_behind()
• dwell sync should be a no-op if no changes are detected
• dwell sync should fail early if no remote is configured
• The dwell.toml config should store the remote URL for dwell sync to use (as an alternative to git remote)

Acceptance criteria

• dwell init --remote <url> creates the repo + sets origin
• dwell sync commits all changes with auto-message
• dwell sync -m "msg" uses custom message
• dwell sync --dry-run shows what would change without committing
• dwell sync pushes to remote after commit
• dwell sync exits cleanly with "nothing to sync" if no changes
• dwell status shows sync status (remote, uncommitted, ahead/behind)
• Integration tests cover init → add → sync → push cycle