feat(cli): add snapshot management commands

[ahosker]

Summary

The Snapshot directory can get very large. This is a simple command to delete it. Its a known issue Also relevent to #1126 #6845 #5617 #3182 #3176

This adds a new snapshot command to manage project snapshot directories with list and clear subcommands.

Changes

• New command: opencode snapshot

  • opencode snapshot list - Lists all projects with snapshot sizes, sorted by size
  • opencode snapshot clear [project-id] - Clears specific snapshot
  • opencode snapshot clear - Clears all snapshots

• Features:

  • Displays project ID, name, size, and last updated date
  • Safety features: --dry-run flag, confirmation prompts by default
  • --force flag to skip confirmation
  • Clear specific project or all projects
  • Error handling for missing projects
  • Success feedback showing space freed

Motivation

Snapshot directories can grow large . Users need a way to:

• See which projects have snapshots and their sizes
• Clean up old or unnecessary snapshots to free disk space
• Manage snapshots per project

I have 8.1 GB across 14 projects.

Testing

# List all snapshots
opencode snapshot list

# Preview what would be deleted (dry-run)
opencode snapshot clear --dry-run

# Clear specific project
opencode snapshot clear <project-id>

# Clear all with confirmation
opencode snapshot clear

# Clear all without confirmation
opencode snapshot clear --force

Code Style

• Follows project style guide (single functions, no destructuring, no else, const only)
• Minimal changes: 2 lines in index.ts + new command file (260 lines)
• All typechecks pass