Improve resume-related actions for resumable sessions

[chumyin]

Summary

Improve resume-related actions for resumable sessions in search results.

Problem

The current search-result actions leave a few gaps:

1. Users can copy a session id, but still need to type the matching CLI resume command manually.
2. Resume in CLI behavior is not consistently available across resumable sources.
3. When resuming in a terminal, the command should open in the original session working directory whenever that directory is still available.

This adds friction and can also drop the user into the wrong working directory before resuming the session.

Proposed behavior

Keep Copy Session ID, and improve the other resume-related actions:

• Add Copy Command beside Copy Session ID for resumable sessions.
• Show Resume in CLI for all session sources that support resume, not just Claude.
• Launch Resume in CLI in the original session working directory when a reliable directory can be resolved.

Examples:

• Claude session: claude --resume <session-id>
• Codex session: codex resume <session-id>

Notes

• Resume actions should be derived from the session source rather than hard-coded to one CLI.
• Copy Command and Resume in CLI should only appear for sources that actually support resume.
• Existing Copy Session ID behavior should remain available.
• Working-directory resolution should prefer the stored session cwd, but fall back safely when that path is missing or no longer exists.

Acceptance criteria

• Search result actions include Copy Command next to Copy Session ID for resumable sessions.
• Clicking Copy Command copies the full resume command, not just the session id.
• Resume in CLI is available for Claude, Codex, and other resumable sources supported by the app.
• Resume in CLI launches in the original session working directory when a valid directory can be resolved.
• If the stored working directory is unavailable, resume still works with a safe fallback instead of failing on a bad cd.
• Non-resumable sources do not show misleading resume actions.

[chumyin]

Implemented in PR #38:

• Improve resume-related actions for session search results #38