bug: --continue flag picks up archived sessions #22175

Description

The --continue flag in both opencode run (CLI) and the TUI picks up archived sessions. If the most recently updated root session has been archived, --continue will resume it instead of finding the next non-archived session.

Use case

Plugin systems can spawn headless agents via opencode run --pure for background tasks (code auditing, knowledge graph ingestion, etc.). These create real sessions in the database that are more recent than the user's interactive session. Archiving them on completion is the natural cleanup path, but --continue currently ignores the archived flag and picks them up anyway. With this fix, plugins can archive background sessions and --continue will correctly skip past them to the user's last interactive session.

Steps to reproduce

1. Create a session and do some work in it
2. Archive the session (via TUI)
3. Run opencode run -c or launch the TUI with --continue
4. The archived session is resumed instead of being skipped

Expected behavior

--continue should skip archived sessions and resume the most recent non-archived root session, consistent with how Session.listGlobal() already filters archived sessions by default.

Actual behavior

--continue uses Session.list() via the /session endpoint, which does not filter archived sessions. The .find() call only checks for parentID === undefined but does not check time.archived.

Environment

• OpenCode version: dev branch (commit 264418c)
• OS: NixOS Linux