[FEATURE]: add projects listing command

[allen-n]

Feature hasn't been suggested before.

• [x] I have verified this feature I'm about to request hasn't been suggested before.

Describe the enhancement you want to request

Summary

Basically, I wanted to know where all the opencode projects on my machine are and which ones have activity, especially when I don’t remember where I have or haven’t used it

Proposal:

• add opencode projects cli command to list known projects with session counts, last activity, and worktree status
• support sorting (path|count|activity), limiting results, and filtering to active projects
• format output with truncated paths and localized timestamps for readability

[allen-n]

I have a PR for this, will link momentarily.

edit: #7546

[github-actions[bot]]

This issue might be a duplicate of existing issues. Please check:

• #7111: Recent projects not found in 'Open Project' dialog search
• #5638: Desktop app: opening multiple git worktrees from the same repo replaces existing project
• #3026: /sessions shows empty despite sessions existing in storage

Feel free to ignore if none of these address your specific case.